Syrovatskyi, V. N. “Functional Models of Commutative Systems of Operators Close to the Unitary”. Visnyk of V. N. Karazin Kharkiv National University. Ser. Mathematics, Applied Mathematics and Mechanics0, no. 1081 (December 16, 2013): 54-66. Accessed April 30, 2024. https://periodicals.karazin.ua/mech_math/article/view/13129.