On (4,2)-Choosable Graphs

Jixian Meng, Gregory J. Puleo, Xuding Zhu

A graph $G$ is called $(a,b)$-choosable if for any list assignment $L$ which assigns to each vertex $v$ a set $L(v)$ of $a$ permissible colours, there is a $b$-tuple $L$-colouring…