@article{MZM_1977_22_2_a3,
     author = {O. I. Reinov},
     title = {Geometric characterization of $RN$-operators},
     journal = {Matemati\v{c}eskie zametki},
     pages = {189--202},
     publisher = {mathdoc},
     volume = {22},
     number = {2},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1977_22_2_a3/}
}