Key points are not available for this paper at this time.
Walberg, Herbert J., and Susan C. Thomas. 1972 Open education: An operational definition and validation in Great Britain and the United States. American Educational Research Journal 9(2): 197-208. Wallach, M. A., and N. Kogan. 1965 Cognitive originality, physiognomic sensitivity and defensiveness in children. Final report to the U. S. Office of Education on Cooperative Research Project No. 131613, Duke University.
Sylvia Polgar (Fri,) studied this question.