Montassier, M., and P. Ochem. “Near-Colorings: Non-Colorable Graphs and NP-Completeness”. The Electronic Journal of Combinatorics 22, no. 1 (March 6, 2015): #P1.57. Accessed May 30, 2026. https://www.combinatorics.org/ojs/index.php/eljc/article/view/v22i1p57.