f^{-1} : G_2 -> G_1 is an isomorphism.
g f : G_1 -> G_3 (the composition) is an isomorphism.
f (1) = 1, and f(x)^{-1} = f(x)^{-1} hold (x in G_1).
ord (f (x)) = ord x holds for x in G_1.
and such that
ord x is finite, for an arbitrary x in G.
Last Updated: 6:43PM, 09/17/06