@article{INTM_1969_a1,
     author = {S. N. Krachkovskii and A. S. Dikanskii},
     title = {Fredholm operators and their generalizations},
     journal = {Itogi nauki i tehniki. Seri\^a, Matemati\v{c}eskij analiz},
     pages = {39--71},
     publisher = {mathdoc},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/INTM_1969_a1/}
}