Plane & spherical trigonometry / [by] Kaj L. Nielsen [and] John H. Vanlonkhuyzen. Nielsen, Kaj Leo, 1914- Vanlonkhuyzen, John H., joint author. Trigonometry. QA531 .N66 1954 514.6 NIP Previous editions published under title: An outline of plane and spherical trigonometry. New York : Barnes & Noble, c1954. c1954. 1954 Text xv, 139 p. : eng College outline series, 45