1. World Health Organization (WHO).
https://www.who.int/news-room/fact-sheets/detail/deafness-and-hearing-loss
2. United Nations (UN).
https://www.un.org/development/desa/disabilities/news/dspd/international-day-sign-languages.html
3. The National Council for Equal Disabilities of Ecuador (CONADIS).
https://www.consejodiscapacidades.gob.ec/estadisticas-de-discapacidad
4. Erting C., Johnson R., Smith D., Snider B.: The Deaf Way: Perspectives from the International Conference on Deaf Culture. Gallaudet University, Washington D.C (1994)
5. Arteaga, K.: Design of a braille manual to improve the reading comprehension in English language directed to children from 7 to 9 years with visual impairments at “CEPE-I” in Ibarra, Ecuador. Pontificia Universidad Católica del Ecuador, Ibarra (2018)