V. M. Adamyan, “Mark Grigorievich Krein (to the centenary of his birth)”, Ukr. Mat. Zhurn., vol. 59, no. 5, pp. 579–587, May 2007, Accessed: Dec. 05, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/3333