R. V. Akopyan, “On the regularity of spectral function of J-unitary J-dissipative operator”, Proceedings of the YSU, Physical and Mathematical Sciences, 1988, no. 2, 22–30
1975
2.
R. V. Akopyan, “Perturbation theory for $J$-positive operators”, Funktsional. Anal. i Prilozhen., 9:2 (1975), 61–62; Funct. Anal. Appl., 9:2 (1975), 142–143
