(VAR x y)
(RULES
  f(a(x), x) -> f(x,a(x))
  f(b(x), x) -> f(x,b(x))
  g(b(x),y) -> g(a(a(x)),y) 
  g(c(x),y) -> y
  a(x) -> b(x) 
)
(COMMENT Example 1 of cite{AYT09})