Revisiting a Theorem by Folkman on Graph Colouring

Marthe Bonamy, Pierre Charbit, Oscar Defrain, Gwenaël Joret, Aurélie Lagoutte, Vincent Limouzy, Lucas Pastor, Jean-Sébastien Sereni
2020 Electronic Journal of Combinatorics  
We give a short proof of the following theorem due to Jon H. Folkman (1969): The chromatic number of any graph is at most $2$ plus the maximum over all subgraphs of the difference between the number of vertices and twice the independence number.
doi:10.37236/8899 fatcat:ot3f2veitzbovjka2r7iz3kgym