Eric Hanushek, «Milton Friedman’s Unfinished Business,» Hoover Digest, Winter 2007.

Haskins and Sawhill, 46.

Margaret Bridges, Bruce Fuller, Russell Rumberger, and Loan Tran, «Preschool for California’s Children: Unequal Access, Promising Benefits,» PACE Child Development Projects, University of California Linguistic Minority Research Institute (September 2004): 9.