Nicolas Werth. “Goulag: les vrais chiffres”. L’Histoire 169 (September 1993), pp. 38–51. More details can be found in J. Arch Getty, Gabor T. Rittersporn and Viktor № Zemskov. Victims of the Soviet Penal System in the Pre-war Years: A First Approach on the Basis of Archival Evidence. The America Historical Review, October 1993, pp. 1017–1049.