as a homework project I received Kernel Graph problem, which is defined as:
Does $G$ possess a kernel, i.e. a subset $W$ of the nodes $V$ such that no two nodes in $W$ are joined by an edge in $A$ and such that for each node $v$ in $V \setminus W$ there is a node $w$ in $W$ for which $(w, v)$ is an edge in $A$?
I would like to read about this problem, therefore I kindly ask you to suggest me some papers on this topic, or maybe different name of the problem, because I can't find much clear information about this problem.