1. International Classification of Impairments, Disabilities and Handicaps (ICIDH-80);World Health Organization,1980
2. International Classification of Functioning, Disability and Health (ICF);World Health Organization,2001
3. A. Colenbrander, Measuring Vision and Vision Loss. vol. 5, Ch. 51 in Duane's Clinical Ophthalmology, Tasman, Jaeger Eds., Lippincot Williams and Wilkins, 2002 edition. See: http://www.ski.org/Colenbrander/.
4. Consultation on Development of Standards for Characterization of Vision Loss and Visual Functioning. WHO, Geneva, 2003. See: http://www.who.int/pbd/blindness/operational_research/en/.
5. A. Colenbrander, Reading Acuity. These conference proceedings.