Poslavskyi , Sergii, and Yuriy Rudnyev. 2021. “I. D. Borisov (obituary)”. Visnyk of V. N. Karazin Kharkiv National University. Ser. Mathematics, Applied Mathematics and Mechanics 93 (June), 37-39. https://doi.org/10.26565/2221-5646-2021-93-05.