Gee, R. D. (1965). Teaching machines and programmed learning: A guide to the literature and other sources of information (2nd ed.). HERTIS.

Gee, Ralph D. Teaching Machines and Programmed Learning: A Guide to the Literature and Other Sources of Information. 2nd ed. Hatfield, Herts.: HERTIS, 1965.

Gee, Ralph D. Teaching Machines and Programmed Learning: A Guide to the Literature and Other Sources of Information. 2nd ed. HERTIS, 1965.