Exploration of the universe / George O. Abell. Abell, George O. (George Ogden), 1927-1983. Astronomy. QB45 .A16 1975 523.1 ABE Includes index. Bibliography: p. 669-671. New York : Holt, Rinehart and Winston, 1975. 1975. 1975 Text xiv, 738 p. : eng