TY  - BOOK
AU  - Boltyanskii,V.G.
TI  - Envelopes
T2  - Popular Lectures in Mathematics; v.12
AV  - MATH QA621.B65 
PY  - 1964///
CY  - Oxford
PB  - Pergamon Press
KW  - Envelopes (Geometry)
ER  -