1. A.H.M. Smets, K. Jäger, O. Isabella, R.V. Swaaij, M. Zeman, Solar Energy: The Physics and Engineering of Photovoltaic Conversion, Technologies and Systems, Kindle edn. (UIT Cambridge Ltd., UK, 2016)
2. U.S. Energy Information Administration, International Energy Outlook 2016-Electricity 0484, 1 (2016).
3. www.eia.gov/forecasts/ieo/pdf/0484(2016).pdf
4. Worldometers, World Population Clock. (2017).
http://www.worldometers.info/world-population/
. Accessed 20 Dec 2019
5. British Petroleum. BP energy outlook. (2017).
https://www.bp.com/content/dam/bp/business-sites/en/global/corporate/pdfs/energy-economics/energy-outlook/bp-energy-outlook-2017.pdf