The Department of Police of the Ministry of Internal affairs : the Fifth Department of the Special Section of the Department of Police (secret unit). The intercepted letters of the Russian revolutionaries, 1883-1917 = Department polit︠s︡ii Ministerstva vnutrennikh del. Pi︠a︡toe otdelenie osobogo otdela departmenta polit︠s︡ii (sekretnai︠a︡ chastʹ). "Perli︠u︡strat︠s︡ii", 1883-1917 (Research Publications an imprint of Primary Source Media, 1998)