First it may be necessary to remind some readers of what is meant by the representation of a group by a Cayley graph. Each element of the group is represented by a point, the points being connected by lines (or edges) each of which represents a generating operation of the group. Suppose, for example, that x and y are two elements of a group, while another element;? is taken as a generator, and that these are connected: xp = y. (Throughout this article we shall take the identity element of a group to be 1, inverses, to be indicated x-1, while xp means “first x, thenp”.) This would be graphed: