Two new block designs

In this note the matrices W, X. Y, and Z are the incidence matrices of the (u, k, ,\,) configurations (15, 7, 3), (25,9,3), (45, 12,3), and (36, 15,6), respectively. Wand X are new formulations of these configurations and Yand Z were previously not known (see [I, pp. 295, 297]).