@article{MZM_1996_59_2_a7,
     author = {N. F. Palinchak},
     title = {About $c$-rigid quadrics},
     journal = {Matemati\v{c}eskie zametki},
     pages = {224--229},
     publisher = {mathdoc},
     volume = {59},
     number = {2},
     year = {1996},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1996_59_2_a7/}
}