1. Statista: The Statistics Portal. Available at https://www.statista.com/statistics/274774/forecast-of-mobile-phone-users-worldwide/. Last access on 10th July 2016. Statista: The Statistics Portal. Available at https://www.statista.com/statistics/274774/forecast-of-mobile-phone-users-worldwide/. Last access on 10th July 2016.
2. United Nations (UN). Available at http://www.un.org/en/globalissues/ageing/index.shtml. Last accessed on 10th Jun 2016. United Nations (UN). Available at http://www.un.org/en/globalissues/ageing/index.shtml. Last accessed on 10th Jun 2016.
3. Ergonomics of human-system interaction ---part 171: Guidance on software accessibility 2008. Ergonomics of human-system interaction ---part 171: Guidance on software accessibility 2008.
4. Brazilian Institute of Geography and Statistics (IBGE) 2015. Available at http://goo.gl/DLhLXV. Last accessed 10th Jun 2016. Brazilian Institute of Geography and Statistics (IBGE) 2015. Available at http://goo.gl/DLhLXV. Last accessed 10th Jun 2016.
5. World Health Organization (WHO) 2015. Available at http://www.who.int/ageing/events/idop_-rationale/en/. Last accessed on 10th Jun 2016. World Health Organization (WHO) 2015. Available at http://www.who.int/ageing/events/idop_-rationale/en/. Last accessed on 10th Jun 2016.