@article{MZM_1999_66_5_a3,
     author = {T. V. Karataeva and V. D. Koshmanenko},
     title = {Generalized sum of operators},
     journal = {Matemati\v{c}eskie zametki},
     pages = {671--681},
     publisher = {mathdoc},
     volume = {66},
     number = {5},
     year = {1999},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1999_66_5_a3/}
}