The authors compiled the information over a two-year investigation that included, but was not limited to,
court documents, affidavits filed by BALCO investigators, confidential memoranda of federal agents (including statements made to them by athletes and trainers), grand jury testimony, audiotapes and interviews with more than 200 sources. Some of the information previously was reported by the authors in the Chronicle. Some of the information is new. For instance,
in an extensive note on sourcing, the authors said memos detailing statements by BALCO owner Victor Conte, vice president James Valente and Anderson to IRS special agent Jeff Novitzky were sealed when they first consulted them, but have been unsealed since.