ABSTRACT
Let G be a groupoid, and let R be a not necessarily associative ring. The groupoid ring R[G] consists of all finite sums where r* G R, gi € G, with addition and multiplication defined by the rules
Theorem 10.1. ([186]) Let G = (V,i£) be an undirected graph without loops and multiple edges. The graph algebra Alg(G) is simple if and only if, for each simple ring R, the groupoid ring R[ Alg{G)\ is simple.
