Real variables / Claude W. Burrill [and] John R. Knudsen. Burrill, Claude W. Knudsen, John R., 1916- joint author. Functions of real variables. QA331.5 .B87 512.81 BUF Includes index Bibliography: p. 411-412. New York, Holt, Rinehart and Winston [1969] [1969] 1969 Text xii, 419 p. : eng