Abashnik, Volodymyr O. “CHRISTOPH SIGWART (1830–1904) AND HIS LOGIC IN THE WORKS OF ISIDOR PRODAN (1854–1919/1920)”. The Journal of V. N. Karazin Kharkiv National University, Series Philosophy. Philosophical Peripeteias0, no. 63 (December 30, 2020): 80-88. Accessed December 5, 2025. https://periodicals.karazin.ua/philosophy/article/view/16617.