1. Facebook statistics, https://www.facebook.com/press/info.php?statistics
2. Aarts, E., de Ruyter, B.: A new research perspectives on ambient intelligence. Journal of Ambient Intelligence and Smart Environments 1(1), 5–14 (2009)
3. Al-Muhtadi, J., Ranganathan, A., Campbell, R., Mickunas, M.: Cerberus: a context-aware security scheme for smart spaces. In: Proceedings of the First IEEE International Conference on Pervasive Computing and Communications, pp. 489–496 (2003)
4. Backstrom, L., Bakshy, E., Kleinberg, J., Lenton, T., Rosenn, I.: Center of attention: How facebook users allocate attention across friends. In: Proceedings of the 5th International AAAI Conference on Weblogs and Social Media (2011)
5. Blumstein, P., Kollock, P.: Personal relationships. Annual Review of Sociology (1988)