Let $G=(V,E)$ be a graph. A subset $Ssubset V$ is a hop dominating setif every vertex outside $S$ is at distance two from a vertex of$S$. A hop dominating set $S$ which induces a connected subgraph is called a connected hop dominating set of $G$. Theconnected hop domination number of $G$, $ gamma_{ch}(G)$, is the minimum cardinality of a connected hopdominating set of $G$...
