1. Ayres, Leonard P.Laggards in Our Schools. New York: Charities Publication Committee, 1909.
2. Time Magazine, 78:(No. 2)58 (July 14, 1961).
3. SeGel, David, and Schwarm, Oscar J. “Retention in High Schools in Large Cities.” United States Department of Health, Education, and Welfare, Bulletin, 1957, No. 15. Washington, D.C.: United States Government Printing Office, 1957.
4. Coplein, Leonard E. “A Study of Retardation and Elimination in the Camden City Public Schools, 1949–1959.” Unpublished doctoral dissertation, Temple University, Philadelphia, Pa., 1961.