@article{DAN_1958_121_2_a4,
     author = {A. Langenbach},
     title = {On the application of the variation principle to some nonlinear differential equations},
     journal = {Doklady Akademii Nauk},
     pages = {214--217},
     publisher = {mathdoc},
     volume = {121},
     number = {2},
     year = {1958},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1958_121_2_a4/}
}