@article{IVM_1975_10_a4,
     author = {F. L. Litvin},
     title = {Determination of the enveloping lines of contact of mutually enveloped surfaces},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {47--50},
     publisher = {mathdoc},
     number = {10},
     year = {1975},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1975_10_a4/}
}