Lykova О. B., “Development of the Bogolyubov-Mitropolsky method of integral varieties”, Ukr. Mat. Zhurn., vol. 44, no. 1, pp. 33–46, Feb. 1992, Accessed: Dec. 06, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/2318