Minimizing the number of edges in $(C_4,K_{1,k})$-co-critical graphs

Gang Chen, Chenchen Ren, Zi-Xia Song

Given graphs $H_1,H_2$, a {red, blue}-coloring of the edges of a graph $G$ is a critical coloring if $G$ has neither a red $H_1$ nor a blue $H_2$. A non-complete graph $G$ is $(H…