1. “Science in the Kindergarten and Early Grades,” Sci. Educ. News, 1–2 (1963).
2. Chemical Bond Approach Project, Chemical Systems, New York, 1964, p. 223.
3. Chemical Bond Approach Project., p. 238.
4. “Children's Ability to Formulate Mental Models to Explain Their Observations of Natural Phenomena,” unpublished Ph.D. dissertation, University of Wisconsin, 1964; Dissertation Abstracts, 25, 3994 (1965).