@article{UZKU_1965_125_1_a3,
     author = {I. V. Zuev},
     title = {A biaxial invariant of a~ruled surface},
     journal = {U\v{c}\"enye zapiski Kazanskogo universiteta. Seri\^a Fiziko-matemati\v{c}eskie nauki},
     pages = {74--78},
     year = {1965},
     volume = {125},
     number = {1},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/UZKU_1965_125_1_a3/}
}