1 Chapman, Clark R. "Mercury." Encyclopedia Britannica. June 7, 2018. Accessed: June 13, 2018.
2 Howell, Elizabeth. "Interesting Facts about Mercury." Universe Today, December 23, 2015. Accessed: June 29, 2018.
3 Redd, Nola Taylor. "What Is Mercury Made Of?" Space.com. October 14, 2016. Accessed: June 28, 2018.
4 Ridpath, Ian, and Wil Tirion. Collins Pocket Guide to Stars and Planets. London: HarperCollins, 1993.
5 Strom, Robert G. Mercury: The Elusive Planet. Washington, DC: Smithsonian Institution Press, 1987.