A. P. Petravchuk, “On Strongly Inert Subalgebras of an Infinite-Dimensional Lie Algebra”, Ukr. Mat. Zhurn., vol. 54, no. 7, pp. 1025–1028, Jul. 2002, Accessed: Dec. 06, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/4143