Boltianskii, V. G. Envelopes / by V.G. Boltyanskii ; translated and adapted from the Russian by Robert B. Brown. - New York : Pergamon Press, 1964. - ix, 76 p. : "A Pergamon Press book." ISBN: 2028 Subjects--Topical Terms: Envelopes (Geometry) Dewey Class. No.: 516 / En