1. World Population Projected to Reach 9.7 Billion by 2050http://www.un.org/en/development/desa/news/population/2015-report.html
2. BP Statistical Review of World Energy, 67th Edition, June 2018https://www.bp.com/content/dam/bp/en/corporate/pdf/energy-economics/statistical-review/bp-stats-review-2018-full-report.pdf
3. BP Energy Outlook, 2018 Editionhttps://www.bp.com/content/dam/bp/en/corporate/pdf/energy-economics/energy-outlook/bp-energy-outlook-2018.pdf