Introduction to probability theory : with contemporary applications / Lester L. Helms. Probability theory Helms, L. L. (Lester La Verne), 1927- Probabilities. QA273 .H52 1997 519.2 20 HEI Includes bibliographical references and index. New York : W.H. Freeman, c1997 c1997 1997 Text x, 351 p. : eng