This report was compiled from numerous sources including government documents, news accounts, and interviews with terrorism experts. In defining who or what constitutes a "terrorist" or "terrorism," washingtonpost.com relied heavily on the judgment of such experts as well as the U.S. government, which maintains a list of those active terrorist groups that either continue to conduct terrorist acts or have conducted them in the past.

Washingtonpost.com would specifically like to thank Vincent Cannistraro, former head of counterterrorist operations at the Central Intelligence Agency and Kenneth Katzman, specialist in Middle Eastern Affairs for the Congressional Research Service for reading texts and providing advice while the report was being compiled.

A complete list of sources follows:

The U.S. Department of State; Central Intelligence Agency; Federal Bureau of Investigation; Bureau of Alcohol, Tobacco, and Firearms; U.S. Department of Treasury, Office of Foreign Assets Control; Embassy of Germany; Embassy of Spain; Embassy of Kuwait; The Terrorist Trap: America's Experience With Terrorism, 1994; America and Iran: Road Maps and Realism, 1998; Office of International Criminal Justice; Patterns of Global Terrorism, 1997 and 1998; Terrorism: Middle Eastern Groups and State Sponsors, 1998; Lethal Terrorist Actions Against Americans, 1973-1986; Terrorism in the United States, 1996; Terrorism Research Center; Conflict Archive on the Internet; Vincent Cannistraro; Kenneth Katzman; Staff Research.

Staff contributions:
Writer: Tim Ito
Database editor: Hal Straus
Producers: Aileen Yoo, Nicole Hider
Editors: Jude Doherty, Jim Sheppard, Douglas Feaver
Photo editors: Jane Menyawi, Gigi Kruse, Tom Kennedy
Additional photo production support: Dee Swann, Amy McNulty, Dyan Elovich
Web technical specialists: Bill Moss, Marcos Lindekugel
Designers: Mark Hill, Paul Compton, Giovanni Calabro
Multimedia: Jude Doherty (writer), Jane Menyawi (producer), Chet Rhodes (narrator)