Dance Is a Contact Sport. By Joseph H. Mazo. Illustrated, 313 pp. New York: Saturday Review Press/E. P. Dutton & Co., Inc., 1974. $10.95; softcover, DaCapo, $5.95. Dance As Life: A Season with American Ballet Theatre. By Franklin Stevens. Illustrated, 190 pp. New York: Harper & Row, 1976. $10.00; softcover, Discus Books, $2.25. Repertory in Review: 40 Years of the New York City Ballet. By Nancy Reynolds. Introduction by Lincoln Kirstein. Illustrated, 358 pp. New York: The Dial Press, 1977. $22.50 Inside American Ballet Theatre. Introduction and Commentaries by Clive Barnes. Illustrated, 184 pp. New York: Hawthorn Books, Inc., 1977. $15.00; softcover, $6.95.