Slyusarchuk VY. Equations in a Hilbert space whose solution sets are invariant with respect to a group isomorphic to a one-parameter group of unitary operators. Ukr. Mat. Zhurn. [Internet]. 2020Jan.15 [cited 2024Apr.25];72(1):86-9. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/687