@article{IM2_1974_8_6_a10,
     author = {I. L. Vulis and M. Z. Solomyak},
     title = {Spectral asymptotics of second-order degenerate elliptic operators},
     journal = {Izvestiya. Mathematics},
     pages = {1343--1371},
     year = {1974},
     volume = {8},
     number = {6},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1974_8_6_a10/}
}