H.J. Klausmeier , M.R. Quilling, J.S. Sorenson, R.S. Way, and G.R. Glasrud, Individually Guided Education and the Multiunit School: Guidelines for Implementation (Madison, Wis.: Wisconsin Research and Development Center for Cognitive Learning, 1971), p. 19.
2.
J.S. Sorenson , M. Poole, L.H. Loyal, The Unit Leader and Individually Guided Education (Reading, Mass.: Addison-Wesley , 1976), p. 393.