@article{FAA_1975_9_2_a8,
     author = {R. V. Akopyan},
     title = {Perturbation theory for $J$-positive operators},
     journal = {Funkcionalʹnyj analiz i ego prilo\v{z}eni\^a},
     pages = {61--62},
     publisher = {mathdoc},
     volume = {9},
     number = {2},
     year = {1975},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/FAA_1975_9_2_a8/}
}