Machniak, A. 2017. Polish military intelligence and counterintelligence activities against the Soviet Union 1918–1939: a description of operations from the files of the main directorate of information of the Polish army . Journal of Humanities and Social Sciences. 2, 1 (Apr. 2017), 27–43. DOI:https://doi.org/10.15584/johass.2017.1.2.