https://www.researchgate.net/profile/Abdu_Gumaei/publication/268924241_Designing_Braille_Copier_Based_on_Image_Processing_Techniques/links/547b36f90cf205d16881c38d.pdf
http://www.saudijgastro.com/article.asp?issn=1319-3767;year=2001;volume=7;issue=1;spage=37;epage=39;aulast=Alam