@article{DAN_1970_194_3_a5,
     author = {N. K. Karapetyants and S. G. Samko},
     title = {The index of certain classes of integral operators},
     journal = {Doklady Akademii Nauk},
     pages = {504--507},
     year = {1970},
     volume = {194},
     number = {3},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1970_194_3_a5/}
}