The article analyzes historiography of the censorship and the problem of source studies practices. It considers the problem of interpretation of the historical source by the researcher M.K. Lemke. The author points out the influence of the researcher's political views on interpretation of historical sources. Based on two works by M. K. Lemke «Essays on the history of Russian censorship and journalism in the XIXth century», «Gendarmery under Nicholas's rule and literature in 1826–1855: On documentary cases of the Third Section of H. I. M. Own Chancery», the author reveals methods of his work with historical and historiographical sources, such as the diary of A. V. Nikitenko and the analytical note by P. K. Schebalsky.