@article{UZKU_1952_112_10_a6,
     author = {M. E. Tsypkin},
     title = {Differential geometry of a~ruled space and its applications to the theory of ruled surfaces},
     journal = {U\v{c}\"enye zapiski Kazanskogo universiteta. Seri\^a Fiziko-matemati\v{c}eskie nauki},
     pages = {77--99},
     publisher = {mathdoc},
     volume = {112},
     number = {10},
     year = {1952},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/UZKU_1952_112_10_a6/}
}