(VAR x y z)
(RULES
*(one, x) -> x
*(i(x), x) -> one
*(*(x, y), z) -> *(x, *(y, z))
f(*(x, y)) -> *(f(x), f(y))
g(*(x, y)) -> *(g(x), g(y))
h(*(x, y)) -> *(h(x), h(y))
k(*(x, y)) -> *(k(x), k(y))
*(f(x), g(y)) -> *(g(y), f(x))
*(f(x), h(y)) -> *(h(y), f(x))
*(h(x), g(y)) -> *(g(y), h(x))
*(f(x), k(y)) -> *(k(y), f(x))
*(k(x), h(y)) -> *(h(y), k(x))
*(k(x), g(y)) -> *(g(y), k(x))
)
(COMMENT Example CGE4 in \cite{WS06})