Levchenko, Natalia, ВozhkoYuliia, Iryna Hontarenko, Liudmyla Baibekova, et Victor Chetveryk. Professor Leonid Ushkalov’s Skovorodiana. Amazonia Investiga 10, no. 43 (août 31, 2021): 105-111. Consulté le mai 19, 2024. https://www.amazoniainvestiga.info/index.php/amazonia/article/view/1686.