@article{DAN_1964_159_2_a8,
     author = {V. K. Romanko},
     title = {Boundary-value problems for operators in two variables with non-homogeneous principal part},
     journal = {Doklady Akademii Nauk},
     pages = {269--272},
     publisher = {mathdoc},
     volume = {159},
     number = {2},
     year = {1964},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1964_159_2_a8/}
}