References
- Erdős, P. (1959). Graph theory and probability. Canad. J. Math. 11: 34–38.
- Lovasz, L. (1968). On chromatic number of finite set-systems. Acta Math. Acad. Sci. Hungar. 19: 59–67.
- Ungar, P., Descartes, B. (1954). Advanced problems and solutions: 4526. Amer. Math. Monthly. 61(5): 352–353. DOI: 10.2307/2307489.
- West, D. B. (2001). Introduction to Graph Theory, 2nd ed. Upper Saddle River, NJ: Prentice-Hall.