1. World Health Organization: Global Age-Friendly Cities: A Guide. World Health Organization, Geneva (2007)
2. Albino, V., Berardi, U., Dangelico, R.M.: Smart cities: definitions, dimensions, performance, and initiatives. J. Urban Technol. 22(1), 3–21 (2015)
3. Caragliu, A., Del Bo, C., Nijkamp, P.: Smart cities in Europe. J. Urban Technol. 18(2), 65–82 (2011)
4. World Health Organization: World Report on Ageing and Health. World Health Organization, Geneva (2015)
5. Statista: Number of smartphone users worldwide from 2014 to 2020 (in billions), June 2016.
https://www.statista.com/statistics/330695/number-of-smartphone-users-worldwide/
. Accessed 15 Dec 2018