1. Bourne, R.R.A., Flaxman, S.R., Braithwaite, T., Cicinelli, M.V., Das, A., Jonas, J.B., et al.: Vision Loss Expert Group: Magnitude, temporal trends, and projections of the global prevalence of blindness and distance and near vision impairment: a systematic review and meta-analysis. Lancet Glob. Health 5(9), e888–e897 (2017)
2. CBP. China Braille Press.
http://www.cdpf.org.cn/sjzx/cjrgk/201206/t20120626_387581.shtml
3. IFIA. International Federation of Inspection Agencies.
www.ifia-federation.org
4. NFB-NEWSLINE. National Federation of the Blind.
https://nfb.org/
5. VisioBook. American Printing House for the Blind.
http://www.aph.org/