All graphs with paired-domination number two less than their order

Let G = (V,E) be a graph with no isolated vertices. A set S ⊆ V is a paired-dominating set of G if every vertex not in S is adjacent with some vertex in S and the subgraph induced by S contains a perfect matching. The paired-domination number Υρ (G) of G is defined to be the minimum cardinality of a paired-dominating set of G. Let G be a graph of order n. In [Paired-domination in graphs, Networks 32 (1998), 199–206] Haynes and Slater described graphs G with Υρ (G) = n and also graphs with Υρ (G) = n − 1. In this paper we show all graphs for which Υρ (G) = n − 2.