I developed these concepts entirely on my own. However, I did use two books to verify two specific numbers related to dark matter issues. In addition, I also used a Scientific American article which discussed more general issues. The three sources have already been cited on the relevant pages, but I list them below for completeness.1. “The Cosmic Cocktail, Three Parts Dark Matter” Katherine Freese, Princeton, NJ, Princeton University Press, 2014. 2. “The Trouble with Physics” by Lee Smolin, Boston & New York, Houghton, Mifflin Company, 2006.3. Hossenfelder, Sabine. McGaugh, Stacy S. “Is Dark Matter Real?”, Scientific American, Aug. 2018, pp 37-43. Print.