Ostrovskii VL, Samoilenko YS. On pairs of unbounded self-adjoint operators satisfying an algebraic relation. Ukr. Mat. Zhurn. [Internet]. 1993Sep.25 [cited 2024Jul.27];45(9):1253–1258. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/5927