@article{MT_1994_24_a4,
     author = {G. V. Demidenko and I. Yu. Nekhaev},
     title = {On the regularity of solutions of boundary value problems for quasi-elliptic equations},
     journal = {Matemati\v{c}eskie trudy},
     pages = {144--166},
     publisher = {mathdoc},
     volume = {24},
     year = {1994},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MT_1994_24_a4/}
}