TY  - JOUR
AU  - V. A. Zalgaller
AU  - F. L. Litvin
TI  - A sufficient criterion for the existence of an envelope of characteristics and a~cuspidal edge on the enveloping surface of a~parametrized family of surfaces
JO  - Izvestiâ vysših učebnyh zavedenij. Matematika
PY  - 1977
SP  - 20
EP  - 23
IS  - 3
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/IVM_1977_3_a2/
LA  - ru
ID  - IVM_1977_3_a2
ER  -