A. K. Bakhtin and A. L. Targonskii, “Some extremal problems in the theory of nonoverlapping domains with free poles on rays”, Ukr. Mat. Zhurn., vol. 58, no. 12, pp. 1715–1719, Dec. 2006, Accessed: Dec. 06, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/3567