Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Let G = (V,E) be a regular graph with v vertices and degree k. G is said to be strongly regular if there are also integers and such that: Every two adjacent vertices have common neighbours. Every two non-adjacent vertices have common neighbours. A graph of this kind is sometimes said to be an srg (v,k, , ). Some authors exclude graphs which satisfy the definition trivially, namely those graphs which are the disjoint union of one or more equal-sized complete graphs, and their complements, the Turán graphs. A strongly regular graph is a distance-regular graph with diameter 2, but only if is non-zero.