1. Number of apps available in leading app stores as of 1 quarter 2019. Retrieved from: https://www.statista.com/statistics/276623/number-of-apps-available-in-leading-app-stores.
2. P. Michaels, “Smartphones with the Longest Battery Life”, tom's guide, June 14, 2019, [viewed online at]https://www.tomsguide.com/us/smartphones-best-battery-life,review-2857.html.
3. D. Ferreira, A. Dey, V. Kostakos, “Understanding human-smartphone concerns: a study of battery life”, In: K. Lyons, J. Hightower, E. Huang (eds) Pervasive Computing. Pervasive 2011. Lecture Notes in Computer Science, vol 6696. Springer, Berlin, Heidelberg
4. Mobile phones and energy consumption;Vasile,2019
5. O. Philippot, “Why should you care about your application's impact on the end user's battery life?” Green Spector, Posted, Dec. 2017