Is the FBI Dragging Its Feet?
                  Barbara Hatch Rosenberg, Federation of American Scientists
                                                           5 February 2002

                  For more than three months now the FBI has known that the perpetrator of the
                  anthrax attacks is American. This conclusion must have been based on the
                  perpetrator's evident connection to the US biodefense program. In addition to
                  this signpost, the perpetrator has left multiple, blatant clues, seemingly on
                  purpose: second letters, addressed similarly to the anthrax letters and
                  containing powder, sent to most (and possibly all) the anthrax recipients;
                  similar letters sent to several other media organizations; even a letter,
                  addressed to the Military Police at the Quantico Marine Base, accusing a
                  former USAMRIID scientist (with whom the anonymous writer says he once
                  worked) of having bioterrorist intentions. Almost all the letters were mailed
                  before there were any reports of anthrax letters or of hoax letters sent to media
                  (see "Analysis of the Anthrax Attacks" below for a chronology and discussion of
                  the available data). The postal addresses and dates of these letters map out an
                  itinerary of the perpetrator(s) and indicate certain connections, which taken
                  together must single out the perpetrator from the other likely suspects.

                  This evidence permits a more refined estimate of the perpetrator's motives. He
                  must be angry at some biodefense agency or component, and he is driven to
                  demonstrate, in a spectacular way, his capabilities and the government's
                  inability to respond. He is cocksure that he can get away with it. Does he know
                  something that he believes to be sufficiently damaging to the United States to
                  make him untouchable by the FBI?

                  The perpetrator is surely too smart to believe that either the FBI's ludicrous
                  recent actions or the White House protestations of ignorance mean that the
                  authorities are not on to him. Blanketing Central New Jersey with fliers showing
                  handwriting that was obviously disguised can't possibly evoke useful
                  information, nor can letters to 32,000 American microbiologists, 31,800 of whom
                  live in a different world from the perpetrator. This is no way to instill public
                  confidence in the competence of the FBI. The press is increasingly questioning
                  the situation, and other scientists have independently raised similar issues
                  (see, for example, "In Search of the Anthrax Attacker"
         Most importantly, the
                  apparent lack of action is sending a dangerous message to potential

                                                  Analysis of the Anthrax Attacks
                                                     Updated 31 JANUARY 2002

                         Barbara Hatch Rosenberg, Federation of American Scientists

                  I. LETTER CHRONOLOGY

                  Four letters with anthrax have been found, and a fifth (to AMI) was apparently
                  discarded after opening. In addition, at least three of the five anthrax recipients
                  also received "hoax" letters containing an innocuous powder; and several
                  different media offices received similar hoax letters. Some of the hoax letters
                  were mailed BEFORE the first anthrax case (in Florida) was reported, and all
                  but one hoax letter were mailed BEFORE there were any reports of anthrax
                  letters or hoax letters. Therefore the hoax letters targeting media are not simply
                  a copycat phenomenon. The envelopes on most or all of the hoax letters were
                  addressed in block capitals similar to the addresses on the anthrax envielopes,
                  even though they were mailed before the anthrax envelopes became known. A
                  photograph of one hoax letter (to St. Petersburg Times) has been published,
                  and descriptions or comparisons of others have been reported. If analysis
                  confirms that the hoax letters were sent by the anthrax perpetrator, their
                  postmarks will indicate his itinerary (or the assistance of an accomplice)-see
                  chronology below.

                  At least three hoax letters, known to have been mailed from St. Petersburg, are
                  similar in many ways to each other and to the anthrax letters: addresses written
                  in similar block capitals, tone of letters, unconvincing misspellings. Were the
                  enclosed letters also xeroxed? no fingerprints? stamps not licked? Are the
                  other hoax letters similar?

                  Furthermore, an anonymous letter accusing a former USAMRIID scientist of
                  plotting terrorism was sent to police BEFORE any anthrax letters or disease
                  were reported. The letter contains evidence that the anonymous writer had
                  probably worked at USAMRIID. This letter may also come from the anthrax

                  Sept. 18, 2001 Trenton
                                      Mailed anthrax letters to NBC and NY Post (and
                                      probably to National Enquirer).
                  Sept. 20, St. Petersburg
                                      Mailed hoax letter to NBC and possibly to NY
                                      Post** [& Natl. Enq.?]
                  Sept. 19-25
                                      NBC received & opened anthrax letter (brown
                                      granular sandy); not recognized as dangerous.
                  Sept. 25
                                     NBC received & opened hoax letter.
                  late Sept.    place?
                                      Mailed letter to Quantico Marine Base accusing Dr.
                                      Asaad, former USAMRIID scientist, as terrorist.
                  Oct. 4
                                     First report of anthrax case (in Florida).
                  Oct. 5
                                      Death of first anthrax victim (in Florida)
                  Oct. 5    St. Petersburg
                                      Mailed hoax letters to J. Miller at NY Times and H.
                                      Troxler at St. Petersburg Times.
                  Oct. 5-9   place?
                                      Mailed hoax letters to CBS (DC), Fox News and
                                      possibly to NY Post**
                  Oct. 9
                                      Troxler (St. Petersburg Times) opened hoax letter.
                  Oct. 9    Trenton
                                      Mailed anthrax letters to Daschle and Leahy.
                  Oct. 12
                                      Miller at NYT opened hoax letter.
                  Oct. 12-13
                                      First reports of any letters to media.
                  Oct. 13
                                      NBC anthrax case and both suspicious letters first
                                      reported. (FBI had previously overlooked events at
                  Oct. 13
                                      CBS News (D.C.) received envelope with powder
                                      visible on outside.
                  Oct. 8-13
                                      Fox News received hoax letter.
                  Oct. 15
                                      Daschle's Hart office opened anthrax letter.
                  Oct. 19
                                      NY Post anthrax case diagnosed and letter with
                                      anthrax found unopened in mailroom. Employee
                                      remembers opening a similarly-addressed (hoax)
                                      letter**, earlier.
                  late Nov.
                                     UK Mailed hoax letter to Dascle office in Capitol.
                  Jan. 3 2002
                                      Daschle's Capitol office opened hoax letter (delay in
                                      receipt due to irradiation of Capitol mail).

                  II. NOTES ON THE LETTERS

                  1. Florida anthrax letter: postal traces show that a letter containing anthrax
                  must have been sent to the National Enquirer at its previous address, then
                  forwarded to the AMI office.
                  This indicates that the perpetrator was not familiar with AMI and the Natl.

                  2. Florida hoax letter?: Possibly a hoax letter was discarded without notice, as
                  the anthrax letter was. In addition, on approximately 4 Sept. AMI received a
                  letter containing powder and a star of David, addressed to actress Jennifer
                  Lopez c/o The Sun (one of the AMI tabloids).

                  3. Hoax letter to NY Post: was received and thrown out sometime before 19
                  Oct. It was addressed to the Editor in block capitals, similar to the anthrax
                  letter received by the NY Post. The NYPost hoax letter could have been mailed
                  on 5 Oct. from St. Petersburg, along with the hoax letters to the NY Times and
                  St. Petersburg Times, or it could have been mailed earlier (eg, on 20 Sept.,
                  when the hoax letter was mailed to NBC). The anthrax letters to NBC and the
                  NY Post had been mailed at the same time (18 Sept) and it is possible that the
                  perpetrator mailed hoax letters on 20 Sept to all of those previously sent

                  4. Hoax letter to NBC: letter contained talcum and was mailed from St. P on 20
                  Sept., two days after the anthrax letter was mailed to NBC from Trenton. Both
                  letters contained threats to Israel.

                  5. Hoax letters to Judith Miller at the NY Times and Howard Troxler at the St.
                  Petersburg Times: these were mailed on 5 Oct. from St. Petersburg and were
                  similar in appearance and content to the NBC hoax letter mailed from St. P on
                  20 Sept. but not yet reported. The NY Times and St. P Times letters were in
                  stamped, plain envelopes with no return address. A photo of the St. P. envelope
                  was published in the St. P Times, showing great similarity to the printing on the
                  anthrax letters (which had not yet been reported-in two cases-or mailed-in the
                  other two cases). The NY Times letter contained talcum and threatened the
                  Sears Tower in Chicago and President Bush. The St P Times letter contained
                  what looked like sugar or salt and said "Howard Toxler...1st case of disease
                  now blow away this dust so you can see how the real thing flys.
                  Oklahoma-Ryder Truck! Skyway bridge-18 wheels."

                  6. Hoax letters to CBS News in Washington, DC and to Fox News: were
                  received on or shortly before 13 Oct. No further information has been reported.
                  They could have been mailed from St. Petersburg on 5 Oct., along with the NY
                  Times and St. P Times letters; or from a place between St. Petersburg and
                  Trenton between 5-9 Oct. Oct. On 12 Oct. an FBI official said they were
                  investigating multiple mailed envelopes from St. Petersburg. The St. Petersburg
                  Police Chief would not comment on whether that included other letters in
                  addition to those sent NBC, NY Times and St. P Times.

                  7. Hoax letter to Senator Daschle: was received and opened by Sen. Daschle's
                  office in the Capitol on 3 Jan. 02, after a delay for irradiation. The letter was
                  mailed from the UK. The envelope contained a powder and a threatening letter
                  unlike those that were mailed with anthrax, according to the FBI. This letter was
                  mailed much later than the others, sometime in late Nov., a month after the
                  other hoax letters and the anthrax letters had been reported. Whether the letter
                  was addressed in block printing, like the anthrax letters, has not been revealed.

                  8. Anonymous letter of accusation: contained a long, typed letter with good
                  command of English language, displaying considerable knowledge of Dr.
                  Assaad, his work at USAMRIID and his personal life and accusing Assaad of
                  planning terrorism. The letter was shown by the FBI to Assaad and his lawyer.
                  The FBI subsequently exhonorated Assaad. The letter, sent to the Marine base
                  at Quantico, VA., asserts that the accuser formerly worked with Assaad. It was
                  sent before any cases of anthrax were discovered.

                  17-31 January 2001

                  1. The Present Situation
                  --The FBI has surely known for several months that the anthrax attack was an
                  inside job. A government estimate for the number of scientists involved in the
                  US anthrax program over the last five years is 200 people. According to a former
                  defense scientist the number of defense scientists with hands-on anthrax
                  experience and the necessary access is smaller, under 50. The FBI has
                  received short lists of specific suspects with credible motives from a number of
                  knowledgeable inside sources, and has found or been given clues (beyond
                  those presented below) that could lead to incriminating evidence. By now the
                  FBI must have a good idea of who the perpetrator is. There may be two factors
                  accounting for the lack of public acknowledgement and the paucity of
                  information being released: a fear that embarrassing details might become
                  public, and a need for secrecy in order to acquire sufficient hard evidence to
                  convict the perpetrator.

                  2. Anthrax Strain
                  --All letter samples contain the same strain of anthrax, corresponding to the
                  AMES strain in the Northern Arizona University database (which has been used
                  for identification). The Ames strain possessed by N. Arizona University is
                  referred to herein as the "reference strain." That strain was obtained by LSU
                  from Porton Down (UK) in 1997 (the sample was marked "10-32" meaning no.
                  10 of 32 samples sent); Porton had gotten it from Fort Detrick. Fort Detrick got
                  it from Texas A&M (but mistakenly attributed it to the USDA laboratory in
                  Ames, Iowa) in 1981. Earlier anthrax isolates from Ames, Iowa have caused
                  some confusion but they are no longer relevant to the situation, thanks to recent
                  genetic analyses (see below).
                  --Contrary to early speculation, there are no more than about 20 laboratories
                  known to have the Ames strain. The names of 15 of these have been found in
                  the open literature (see Appendix). Of these, probably only about four in the US
                  might possibly have the capability for weaponizing anthrax. Those four include
                  both US military laboratories and a government contractor.
                  --Genetic analysis performed at Northern Arizona University on Ames strain
                  samples from Fort Detrick (USAMRIID), Dugway Proving Ground, the UK
                  defense establishment at Porton, Louisiana State University and Northern
                  Arizona University has shown that all of these laboratories possess identical
                  anthrax stocks that match the letter anthrax perfectly (in the limited analyses
                  that have been done). All these stocks were originally derived from Fort
                  Detrick's 1980 Ames strain. USAMRIID acknowledges that it also provided
                  Ames to the Canadian defense establishment at Suffield, the University of New
                  Mexico, and Battelle Memorial Institute (a large contracting organization with
                  laboratories and personnel in many locations including military laboratories).
                  Excluding the three academic institutions, two of which are intimately involved
                  in the investigation, and the two foreign defense laboratories, places the focus
                  on USAMRIID, Dugway and Battelle as the source of the Ames strain for the
                  --The complete sequence has been determined for the genomes of both the
                  anthrax used in the Florida attack and the Ames reference strain to which it
                  corresponds. This work was done under government contract by the Institute for
                  Genetic Research, a private non-profit organization. The results have not been
                  made public but they are in government hands and there has been no retraction
                  of the oft-repeated official statement that the letter anthrax matches the Ames
                  reference strain.
                  --Analysis of trace contaminants in the letter anthrax has probably been carried
                  out but not reported. The results could indicate whether the anthrax was grown
                  in liquid medium (and what kind of medium), or on petri dishes; the latter would
                  likely rule out large-scale preparation. It has been estimated that the perpetrator
                  used a total of about 10g in the letters.

                  3. Anthrax Weaponization
                  --"Weaponization" is used here to mean preparation of the form of anthrax found
                  in the Daschle letter: fine particles, very narrow size range, treated to eliminate
                  static charge so it won't clump and will float in the air. The weaponization
                  process used was extraordinarily effective. The particles have a narrow size
                  range (1.5-3 microns diameter), typical of the optimal US process.
                  --The extraordinary concentration (one trillion spores per gram) and purity of the
                  letter anthrax is believed to be characteristic of material made by the optimal
                  US process.
                  --The optimal US weaponization process is secret-Bill Patrick, its inventor,
                  holds five secret patents on the process and says it involves a combination of
                  chemicals . There is no evidence that any other country possesses the formula.
                  --Under the microscope, the letter anthrax appears to be unmilled. Milled
                  anthrax spores are identifiable because they contain debris. The optimal US
                  process does not use milling.
                  --The Daschle sample contains a special form of silica used in the US process.
                  It does not contain bentonite (used by the Iraqis).
                  --A "coating" on the spores in the letter sample, indicative of the secret US
                  process, has been observed.
                  --The Armed Forces Institute of Pathology in Washington, DC has studied the
                  sample using an energy dispersive X-ray specroscope, which can detect the
                  presence of extremely tiny quantities of chemicals; traces of several chemicals
                  have been found (but not reported, presumably for security reasons).
                  --All the letters probably contained the same material. The clumping of the
                  anthrax in the two letters mailed on Sept 18 (to NBC and the NY Post) probably
                  resulted from the letters getting wet in the course of mail processing or delivery,
                  according to Army scientists. This conclusion is strengthened by the similarity
                  of the Florida anthrax (the first to be observed, probably also mailed on Sept 18)
                  to that in the Daschle letter, mailed Oct 9.
                  --The letter anthrax was made after 1980 (when the Ames strain used was
                  obtained) using a process similar to the secret, optimal US process. If the
                  anthrax was weaponized by the perpetrator himself, there may be some
                  differences from anthrax weaponized by the government, depending on the
                  availability of materials to the perpetrator and the conditions of preparation.

                  4. Other Clues
                  --Scientists formerly at USAMRIID say that it would have been easy for a
                  scientist working with anthrax to remove a sample of the Ames strain from the
                  lab. Only a miniscule amount would be needed, and security has been lax.
                  --On the other hand, experts believe that it would be extremely difficult to steal
                  10g of weaponized anthrax from a government lab. Thus, the perpetrator very
                  likely grew and weaponized the letter anthrax himself.
                  --There was only one week between Sept 11 and Sept 18, when the first two
                  letters (and probably another letter, never found, to AMI) were postmarked. This
                  suggests that the anthrax was already in hand, and the attack largely planned,
                  before Sept 11.
                  --A classified report dated February, 1999 discusses responses to an anthrax
                  attack through the mail. The report, precipitated by a series of false anthrax
                  mailings, was written by William Patrick, inventor of the US weaponization
                  process, under a CIA contract to SAIC. The report describes what the US
                  military could do and what a terrorist might be able to achieve. According to the
                  NY Times (12 Dec. 01) the report predicted about 2.5g of anthrax per envelope
                  (the Daschle letter contained 2g) and assumed a poorer quality of anthrax than
                  that found in the Daschle letter. If the perpetrator had access to the materials
                  and information necessary for the attack, he must have had security clearance
                  or other means for accessing classified information, and may therefore have
                  seen the report and used it as a model for the attack.
                  --An anonymous letter was sent to police, apparently in September, accusing
                  an Egyptian-born American scientist who had been laid off by USAMRIID of
                  being a terrorist. The FBI questioned and released the accused scientist as
                  innocent. Details of the letter have not been released. Could this letter have
                  been sent by the perpetrator (who would likely have known about the USAMRIID
                  lay-offs) to cover his traces?
                  --The perpetrator did not aim to kill but to create public fear. The letters warned
                  of anthrax or the need to take antibiotics, making it possible for those who
                  handled the letters to protect themselves; and it is unlikely that the perpetrator
                  would have anticipated that the rough treatment of mail in letter sorters, etc,
                  would force anthrax spores through the pores of the envelopes (which were
                  taped to keep the anthrax inside) and infect postal workers and others.
                  --The perpetrator was probably ready before Sept. 11 and simply took advantage
                  of the likelihood that Sept. 11 would throw suspicion on Muslim terrorists. Was
                  the perpetrator trying to push the US toward some retaliatory military action?
                  --The perpetrator must have realized in advance that the anthrax attack would
                  result in the strengthening of US defense and response capabilities. This is not
                  likely to have been a goal of anti-American terrorists, who would also be unlikely
                  to warn the victims in advance. Perhaps the perpetrator stood to gain in some
                  way from increased funding and recognition for biodefense programs. Financial
                  beneficiaries would include the BioPort Corp., the source of the US anthrax
                  vaccine, and other potential vaccine contractors.
                  --Expert analysts for the FBI believe that the letters were written by a
                  Westerner, not a Middle Easterner or Muslim, although the text was clearly
                  intended to imply the latter.
                  --The choice of a variety of media as targets seems to have been cleverly
                  designed to ensure a broad spectrum of publicity about the attacks. The choice
                  of Senators Daschle and Leahy suggests that the perpetrator may lean to the
                  political right and may have some specific grudge against those Senators.
                  --The perpetrator successfully covered every personal trace when he prepared
                  and mailed the letters, which suggests that he had forensic training or
                  --Even if the perpetrator did not make the anthrax himself, just filling the letters
                  with it was a dangerous operation. The perpetrator therefore must have received
                  the anthrax vaccine recently (it requires a yearly booster shot). The vaccine is in
                  short supply and is not generally accessible, and vaccination records are
                  undoubtedly available. The perpetrator also appears to have special expertise in
                  evading contamination while handling weaponized anthrax.

                  5. Government Statements, Actions and Chronology
                  --On 13 Jan. 02 Homeland Security Director Thomas Ridge said "the primary
                  direction of the investigation is turned inward" toward domestic terrorists.
                  --On 2 Dec. 01 a law enforcement official close to the federal investigation called
                  the concept of a government insider, or someone in contact with an insider, "the
                  most likely hypothesis…it's definitely reasonable." Another American official
                  was quoted in the same article saying that, in addition to military laboratories,
                  "there are other government and contractor facilities that do classified work with
                  access to dangerous strains, but it's highly likely that the material in the
                  anthrax letters came from a person or persons who really had great expertise.
                  We haven't seen any other artifacts that point us elsewhere."
                  --Secret or questionable biodefense projects tend to be given to the CIA, DOE
                  or other agencies and contractors instead of to DOD, in order to maintain
                  deniability (for example, only DOD programs have been reported by the US in
                  the annual information exchange about biodefense activities, under the
                  Biological Weapons Convention). Many contractor scientists work in
                  government labs. A CIA spokesman says that CIA scientists work with other
                  government agencies and contractors on the biodefense program.
                  --Chronology: Analytical data on the anthrax in the letters became available to
                  investigators in late October, 2001. The FBI then began questioning former
                  government scientists. On 31 Oct. it was reported that the US rejected a UN
                  resolution offered by France to condemn the anthrax attack, on the grounds that
                  it could have been domestic terrorism. On 9 Nov. the FBI released a profile of
                  the perpetrator as a lone, male domestic terrorist, obviously one with a scientific
                  background and laboratory experience who could handle hazardous materials.
                  In early Dec. the FBI said it was investigating government and contractor labs
                  possessing the Ames strain, and individuals who had access to them. On 16
                  Dec. the FBI said it was focusing on a contractor that worked with the CIA. At
                  about the same time the FBI said it was interested in non-military individuals
                  who had received the anthrax vaccine.
                  --John Bolton, Under Secretary of State for Arms Control and International
                  Security, said on 19 Nov. that "We don't know…at the moment, in a way that
                  we could make public, where the anthrax attacks came from." Senate Majority
                  Leader Thomas Daschle, recipient of one of the anthrax letters and in frequent
                  contact with investigators, said on 8 Dec. that the perpetrator was probably
                  someone with a military background. Ari Fleischer, the White House
                  spokesman, said on 17 Dec. that it is increasingly "looking like it was a
                  domestic source."
                  --After a series of uncontrolled statements to the media, relevant experts have
                  been asked to keep quiet and, in some cases, appear to have been asked to
                  "correct" former statements.

                  6. Possible Portrait of the Anthrax Perpetrator
                  --Insider in US biodefense, doctoral degree in a relevant branch of biology
                  --Middle-aged American
                  --Experienced and skilled in working with hazardous pathogens, including
                  anthrax, and avoiding contamination
                  --Works for a CIA contractor in Washington, DC area
                  --Has up-to-date vaccination with anthrax vaccine
                  --Has clearance for access to classified information
                  --Worked in USAMRIID laboratory in the past, in some capacity, and has
                  access now
                  --Knows Bill Patrick and has probably learned a thing or two about
                  weaponization from him, informally
                  --Has had training or experience in covering evidence
                  --May have had an UNSCOM connection
                  --Has had a dispute with a government agency
                  --Has a private location where the materials for the attack were accumulated
                  and prepared
                  --Worked on the letters alone or with peripheral encouragement and assistance
                  --Fits FBI profile
                  --Has the necessary expertise, access and a past history indicating appropriate
                  capabilities and temperament
                  --Has been questioned by FBI

                  --A recent report by the Congressional General Accounting Office, as well as
                  many recent statements by military and non-governmental experts in the BW
                  field, holds that terrorists are unlikely to be able to mount a major biological
                  attack without substantial assistance from a government sponsor. The recent
                  anthrax attack was a minor one but nonetheless we now see that it was made
                  possible by a sophisticated government program. It is reassuring to know that it
                  was probably not perpetrated by a lone terrorist without state support.
                  --It is not reassuring, however, to discover that secret US programs may have
                  been the source of that support, and that security is so dangerously lax in
                  military or defense contractor laboratories. US government insistence on
                  pursuing and maintaining the secrecy of elaborate biological threat assessment
                  activities is undermining the prohibitions of the Biological Weapons Convention
                  and encouraging biological weapons proliferation in other countries, which in
                  turn may support bioterrorist attacks on the American public. Future deterrence,
                  and the peace of mind of the American people, require that the perpetrator must
                  be publicly identified and brought to justice without delay.


                  (Information obtained from open sources)
                  1. USAMRID # +
                  2. Dugway Proving Ground (Utah) # * +
                  3. Naval Research Medical Center and associated military labs (MD) #
                  4. Battelle Memorial Institute (Ohio; plus laboratories in many other locations) #
                  * +
                  5. Duke University Medical School, Clinical Microbiology Lab (NC)
                  6. VA Medical Center, Durham (NC)
                  7. USDA laboratory and Iowa State College of Veterinary Medicine, Ames
                  8. LSU College of Veterinary Medicine * +
                  9. Northern Arizona State University (Arizona) * +
                  10. Illinois Institute of Technology Research Institute (IL)
                  11. University of New Mexico Health Sciences Center, Albuquerque (NM) * +
                  12. Chemical and Biological Defense Establishment, Porton Down (UK) * +
                  13. CAMR, Porton (UK) *
                  14. Defense Research Establishment, Suffield (CA) * +
                  15. BioPort Corp (MI)
                  In addition, CDC, NIH, Los Alamos and a few others may have the Ames strain;
                  the Institute for Genomic Research (MD) says they have the Ames DNA but not
                  the bacteria.
                  # indicates laboratories in the US that are estimated to be more likely than the
                  others to have weaponization capabilities
                  * Obtained through a FOIA request by the Washington Post (article Nov 30, 01)
                  + indicates acknowledged recipients of the Ames strain from USAMRIID

                  Contact: Barbara Hatch Rosenberg, PhD
                  Chair, Federation of American Scientists Working Group on Biological
                  Professor, SUNY-Purchase