Announced on August 17 and published on October 10, 1971, this four-volume, relatively expensive set became the "Senator Gravel Edition," which studies from Cornell University and the Annenberg Center for Communication have labeled as the most complete edition of the Pentagon Papers to be published. The "Gravel Edition" was edited and annotated by Noam Chomsky and Howard Zinn, and included an additional volume of analytical articles on the origins and progress of the war, also edited by Chomsky and Zinn. Beacon Press became the subject of an FBI investigation, an outgrowth of which was "Gravel v. United States" in which the U.S. Supreme Court ruled in June 1972 that the Speech or Debate Clause in the US Constitution did grant immunity to Gravel for his reading the papers in his subcommittee, and did grant some immunity to Gravel's congressional aide, but granted no immunity to Beacon Press in relation to its publishing the same papers.