@article{DAN_1957_113_4_a2,
     author = {M. I. Vishik and L. Lusternik},
     title = {On elliptical equations containing small parameters in the terms with higher derivatives},
     journal = {Doklady Akademii Nauk},
     pages = {734--737},
     publisher = {mathdoc},
     volume = {113},
     number = {4},
     year = {1957},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1957_113_4_a2/}
}