On the structure of connected locally GQ(3,9)-graphs Original Research Article

If F is a class of graphs then a graph Γ is called a locally F-graph, provided that the neighborhood of every vertex of Γ belongs to F. Let GQ(s,t) denote the point graph of a generalized quadrangle of order (s,t). We prove that every connected locally GQ(3,9)-graph is isomorphic to the McLaughlin graph.