Kragujevac J. Math. 24 (2002) 43-53.
Mirko Lepovic
Department of Mathematics, Faculty of Science, University of
Kragujevac,
34000 Kragujevac, Yugoslavia
(Received February 25, 2002)
Abstract. Let G be a simple connected or disconnected graph which has exactly two main eigenvalues. Let Gk = G \ k be the corresponding vertex deleted subgraph of G. If Gi and Gj are cospectral in this paper we prove that their complementary graphs Gi and Gj are also cospectral.