@article{DAN_1957_112_3_a5,
     author = {R. N. Shcherbakov},
     title = {Projective invariant marks of a ruled surface belonging to a given congruence},
     journal = {Doklady Akademii Nauk},
     pages = {390--393},
     publisher = {mathdoc},
     volume = {112},
     number = {3},
     year = {1957},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1957_112_3_a5/}
}