(VAR )
(RULES
  g(f(a)) -> f(g(f(a)))
  g(f(a)) -> f(f(a))
  f(f(a)) -> f(a)
)
(COMMENT
doi:10.1016/0890-5401(90)90015-A
[24] p. 188
submitted by: Takahito Aoto, Junichi Yoshida, and Yoshihito Toyama
)