Hertz, Alain, and Bernard Ries. “A Note on R-Equitable K-Colorings of Trees”. Yugoslav Journal of Operations Research 24, no. 2 (June 1, 2014): 293–298. Accessed August 26, 2025. https://yujor.erc.fon.bg.ac.rs/index.php/yujor/article/view/397.