@article{IVM_1999_11_a7,
     author = {K. B. Sabitov and A. A. Karamova and G. G. Sharafutdinova},
     title = {On the theory of equations of mixed type with two lines of degeneration},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {70--80},
     publisher = {mathdoc},
     number = {11},
     year = {1999},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1999_11_a7/}
}