1. Beecher, H. K.: Measurement of Subjective Responses: Quantitative Effects of Drugs. New York, Oxford, 1959.
2. Experimental studies of fatigue of accommodation: II;Berens;Am. J. Ophth.,1950
3. Reading and Visual Fatigue;Carmichael,1947
4. Medical progress; Popular misconceptions pertaining to ophthalmology;Cogan;New Engl. J. Med.,1941
5. Donders, F. C.: Anomalies of Accommodation and Refraction of the Eye. 1864.