References

Gapminder.org. 2021. “Free Data from World Bank via Gapminder.org, CC-BY License.” 2021. https://www.gapminder.org/data/.
Ross, Sheldon M. 2017. “Introductory Statistics.” In Introductory Statistics (Fourth Edition), edited by Sheldon M. Ross, Fourth Edition, 797–800. Oxford: Academic Press. https://doi.org/https://doi.org/10.1016/B978-0-12-804317-2.00031-X.
Venables, W. N., and B. D. Ripley. 1999. Modern Applied Statistics with s-Plus. 3rd ed. New York: Springer-Verlag.