@article{DAN_1972_203_5_a10,
     author = {A. Yanushauskas},
     title = {A reduction of a directional derivative problem},
     journal = {Doklady Akademii Nauk},
     pages = {1014--1017},
     publisher = {mathdoc},
     volume = {203},
     number = {5},
     year = {1972},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1972_203_5_a10/}
}