@article{DAN_1962_144_5_a11,
     author = {R. R. Mullari},
     title = {On the principle directions of an $m$-dimensional surface},
     journal = {Doklady Akademii Nauk},
     pages = {989--992},
     publisher = {mathdoc},
     volume = {144},
     number = {5},
     year = {1962},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1962_144_5_a11/}
}