1. Marion, G., & Lawson, D. (2015). An Introduction to Mathematical Modelling.
2. Weisstein, Eric W. “e”. mathworld.wolfram.com. Retrieved May 5, 2021.
3. Estimated Median Age at First Marriage by Sex: 1980 to the Present. United States Census Bureau. https://www.census.gov/data/tables/time-series/demo/families/marital.html
4. Abdulhafedh, A. (2020). Highway Stopping Sight Distance, Decision Sight Distance, and Passing Sight Distance Based on AASHTO Models. Open Access Library Journal, 7, 1–24. https://doi.org/10.4236/oalib.1106095