Потоцький, В’ячеслав. 2016. “Polish Captain Andrzej Okun’s Role in the Military Campaigns Against the Ukrainian Cossacks (1648 – Beginning of the 50s of the ХVII Century)”. V. N. Karazin Kharkiv National University Bulletin ‘History of Ukraine. Ukrainian Studies: Historical and Philosophical Sciences’ 21 (September), 21-29. https://periodicals.karazin.ua/uahistory/article/view/6049.