(VAR x y)
(RULES
  h(f,a,a) -> h(g,a,a)
  h(g,a,a) -> h(f,a,a)
  a -> a'
  h(x,a',y) -> h(x,y,y)
  g -> f
  f -> g
)
(COMMENT
[17] Example 4
submitted by: Takahito Aoto, Junichi Yoshida, and Yoshihito Toyama
)