1. New design principles for visual acuity letter charts;Bailey;Am. J. Optom. Physiol. Opt.,1976
2. Recommended standard procedures for the clinical measurement and specification of visual acuity;NAS-NRC Committee on Vision;Adv. Ophthalmol.,1980
3. Early Treatment Diabetic Retinopathy Study: Manual of Operations. Baltimore, ETDRS Coordinating Center, Department of Epidemiology and Preventive Medicine, 1980, ch. 12, pp. 1–15.
4. Comparison of three types of test target for the measurement of visual acuity;Sloan;Q. Rev. Ophthalmol.,1952
5. From 20/20 to 6/6 or 4/4;Hofstetter;Arch. Am. Acad. Optom.,1973