Graph designs for the eight-edge five-vertex graphs

The existence of graph designs for the two nonisomorphic graphs on five vertices and eight edges is determined in the case of index one, with three possible exceptions in total. It is established that for the unique graph with vertex sequence (3, 3, 3, 3, 4), a graph design of order n exists exactly when n equivalent to 0.1 (mod 16) and n not equal 16, with the possible exception of n = 48. For the unique graph with vertex sequence (2, 3, 3, 4, 4), a graph design of order n exists exactly when n equivalent to 0, 1 (mod 16), with the possible exceptions of n is an element of {32, 48}. (C) 2008 Elsevier B.V. All rights reserved.