Levchenko, N., Вozhko Y., Hontarenko, I., Baibekova, L. and Chetveryk, V. 2021. Professor Leonid Ushkalov’s Skovorodiana. Amazonia Investiga. 10, 43 (Aug. 2021), 105–111. DOI:https://doi.org/10.34069/AI/2021.43.07.10.