I guess he means taking the direct product of a group G and a group H, where G is already known to be a direct product of two groups A and B , and H is just another group: i.e. G x H. In this case, the direct product isn't anything more special, as G x H = A x B x H since ( A x B ) x H = A x ( B x H ) .. et c. Then, you can write ( a, b, h ) where a is in A , b is in B and h is in H. Just think about R^3 = R x R^2