2 citations to https://www.mathnet.ru/eng/emj251

1. B. D. Djordjevic, “On a singular sylvester equation with unbounded self-adjoint a and B”, Complex Anal. Oper. Theory, 14:4 (2020), 43          
2. A. K. Motovilov, A. A. Shkalikov, “Sokhranenie svoistva bezuslovnoi bazisnosti pri nesamosopryazhennykh vozmuscheniyakh samosopryazhennykh operatorov”, Funkts. analiz i ego pril., 53:3 (2019), 45–60