Lyst-klopotannja M. Kostomarova do ministra narodnoï osvity, hrafa D. Tolstoho pro dozvil studijuvaty archivni materialy z "Ystoryy Puhačevskoho bunta" ta oficijna vidpovidʹ (do žyttjepysu kabinetnoho včenoho počatku 1870-ch rokiv) = Mykola Kostomarov's letter to count Tolstoy requesting permission to study archival materials relating to the Pugachov rebellion and the official reply : (on the biography of the private scholar of the early 1870s) - Jasʹ, Oleksij Vasylʹovyč 1967- (2018)