Clifford A. Pickover: A Passion for Mathematics: Numbers, Puzzles, Madness, Religion, and the Quest for Reality. Wiley, 2011, ISBN9781118046074, S. 33 (excerpt, p. 33, at Google Books)
chesscafe.com
Kingston, Taylor. "Your Morphy Number Is Up"(PDF). Chesscafe. Archived(PDF) from the original on 13 June 2006. Retrieved 9 December 2020.
López de Prado, Marcos (2016). "Mathematics and Economics: A reality check". The Journal of Portfolio Management. 43 (1): 5–8. doi:10.3905/jpm.2016.43.1.005. S2CID219231926.
López de Prado, Marcos (2016). "Mathematics and Economics: A reality check". The Journal of Portfolio Management. 43 (1): 5–8. doi:10.3905/jpm.2016.43.1.005. S2CID219231926.