@article{MAT_1970_14_4_a2,
     author = {L. V. H\"ormander},
     title = {On the index of pseudodifferential operators},
     journal = {Matematika},
     pages = {78--97},
     year = {1970},
     volume = {14},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MAT_1970_14_4_a2/}
}