1. Balliwalla, Low Vision—Assessment and Aids, Bombay Hospital Journal http://www.bhj.org/journal/2002_4403_jul/md_397.htm , 2002
2. Maeda Y, Tano E, Makino H, Konishi T, Ishii I (2002) Evaluation of a GPS-based guidance system for visually impaired pedestrians. In: Technology and persons with disabilities conference 2002. March 18–23, Los Angeles, California, USA
3. May M (2000) Accessible GPS navigation and digital map information for blind consumers. ICWC
4. Strothotte T, Fritz S, Michel R, Raab A, Petrie H, Johnson V, Reichert L, Schalt A (1996) Development of dialogue systems for the mobility aid for blind people: initial design and usability testing. ASSETS ’96, Vancouver, British Columbia, Canada, pp 139–144
5. Golledge RG, Klatzky RL, Loomis JM, Speigle J, Tietz J (1998) A geographical information system for a GPS based personal guidance system. Int J Geograph Inform Sci 12(7):727–749