"The Gulag Archipelago" was composed from 1958 to 1967, and has sold over thirty million copies in thirty-five languages. It was a three-volume, seven-part work on the Soviet prison camp system, which drew from Solzhenitsyn's experiences and the testimony of 256 former prisoners and Solzhenitsyn's own research into the history of the Russian penal system. It discusses the system's origins from the founding of the Communist regime, with Vladimir Lenin having responsibility, detailing interrogation procedures, prisoner transports, prison camp culture, prisoner uprisings and revolts such as the Kengir uprising, and the practice of internal exile. Soviet and Communist studies historian and archival researcher Stephen G. Wheatcroft wrote that the book was essentially a "literary and political work", and "never claimed to place the camps in a historical or social-scientific quantitative perspective" but that in the case of qualitative estimates, Solzhenitsyn gave his high estimate as he wanted to challenge the Soviet authorities to show that "the scale of the camps was less than this." Historian J. Arch Getty wrote of Solzhenitsyn's methodology that "such documentation is methodically unacceptable in other fields of history", which gives priority to vague hearsay and leads towards selective bias. According to journalist Anne Applebaum, who has made extensive research on the Gulag, "The Gulag Archipelago"'s rich and varied authorial voice, its unique weaving together of personal testimony, philosophical analysis, and historical investigation, and its unrelenting indictment of Communist ideology made it one of the most influential books of the 20th century.