1. World population prospects: the 2015 revision. Key findings and advance tables. Retrieved from http://esa.un.org/unpd/wpp/publications/files/key_findings_wpp_2015.pdf.
2. Ki-Moon B. Big idea 2014: the year for climate action. Retrieved from http://www.un.org/climatechange/summit/2013/12/big-idea-2014-the-year-for-climate-action-by-ban-ki-moon/.
3. The imperative of disruptive innovation. Retrieved from http://www.innosight.com/innovation-resources/upload/Disruptive-Innovation-Primer.pdf.
4. Innovative sustainable practices: are they commercially viable?;El-Kafafi;World J Entrep Manag Sustain Dev,2010
5. Brundtland G, Khalid M, Agnelli S, et al. Report of the world commission on environment and development: our common future. Retrieved from http://www.un-documents.net/our-common-future.pdf.