@article{RM_1970_25_4_a3,
     author = {M. I. Vishik and V. V. Grushin},
     title = {Degenerating elliptic differential and psevdo-differential operators},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {21--50},
     publisher = {mathdoc},
     volume = {25},
     number = {4},
     year = {1970},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/RM_1970_25_4_a3/}
}