@article{MZM_1997_61_2_a12,
     author = {A. D. Ioffe and V. M. Tikhomirov},
     title = {Some remarks on variational principles},
     journal = {Matemati\v{c}eskie zametki},
     pages = {305--311},
     publisher = {mathdoc},
     volume = {61},
     number = {2},
     year = {1997},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1997_61_2_a12/}
}