1. Testing of visual acuity in pre-school children: norms, variables and a new picture test;Allen;Paediatrics,1957
2. Assessment of visual ability in the profoundly handicapped;Bell;National Association of Deaf and Blind Rubella Handicapped Newsletter,1983
3. A comparative study of visual acuity test for children;Borg;Acta Ophthalmologica,1967