Vaskouski, Maksim M., et al. “A Generalisation of the Steiner – Lehmus Theorem and Critical Values Transcendence of Its Parameters”. Journal of the Belarusian State University. Mathematics and Informatics, no. 2, Nov. 2025, pp. 42-61, https://doi.org/10.33581/2520-6508-2025-2-42-61.