@article{SM_1977_32_1_a2,
     author = {V. V. Grushin and N. A. Shananin},
     title = {Some theorems on the singularities of solutions of differential equations with weighted principal symbols},
     journal = {Sbornik. Mathematics},
     pages = {32--44},
     publisher = {mathdoc},
     volume = {32},
     number = {1},
     year = {1977},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1977_32_1_a2/}
}