@article{DAN_1957_114_4_a6,
     author = {\"U. G. Lumiste},
     title = {On surfaces $V_n$ with multidimensional isotropic conjugate directions in spaces $R_N$ or $S_N$},
     journal = {Doklady Akademii Nauk},
     pages = {702--705},
     publisher = {mathdoc},
     volume = {114},
     number = {4},
     year = {1957},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1957_114_4_a6/}
}