Duke-Elder, Sir W. S.1946. Textbook of ophthalmology. Vol. 1. C. V. Mosby Co.
2.
Getman, G. N.1971. Early identification of the interfering visual problems. In Learning to see and seeing to learn, ed. R. C. Orem.Johnstown, Pennsylvania: Mafex Associates.
3.
Greenstein, T.1971. What an adequate visual examination should include. In Learning to see and seeing to learn, ed. R. C. Orem.Johnstown, Pennsylvania: Mafex Associates.
4.
Harmon, D. B.1958. Notes on a dynamic theory of vision. Austin, Texas: published by the author.
5.
Henry, W. R.1971. Relationships of the visual functions investigated to the learning process in the young child. In Learning to see and seeing to learn, ed. R. C. Orem. Johnstown, Pennsylvania: Mafex Associates.
6.
Kephart, N. C.1960, 1971. The slow learner in the classroom. Columbus, Ohio: Charles E. Merrill Books.
7.
McQuarrie, C. W. (comp.). 1967. A perceptual testing training guide for kindergarten teachers. Winter Haven, Florida: Winter Haven Lions Research Foundation.
8.
Pierce, J.1966–1968. Research on the relationship between near-point lenses, human performance, and physiological activity of the body. Duncan, Oklahoma: Optometric Extension Program Foundation.