@article{FAA_1977_11_2_a10,
     author = {A. S. Markus and I. A. Fel'dman},
     title = {Index of an operator matrix},
     journal = {Funkcionalʹnyj analiz i ego prilo\v{z}eni\^a},
     pages = {83--84},
     publisher = {mathdoc},
     volume = {11},
     number = {2},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/FAA_1977_11_2_a10/}
}