@article{DAN_1963_149_5_a6,
     author = {G. S. Litvinchuk},
     title = {On the index and normal solvability of a class of functional equations},
     journal = {Doklady Akademii Nauk},
     pages = {1029--1032},
     publisher = {mathdoc},
     volume = {149},
     number = {5},
     year = {1963},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1963_149_5_a6/}
}