(VAR x)
(RULES
  f(x,x) -> a
  c -> h(c,g(c))
  h(g3(x), g1(g2(x)))-> f(x,h(x,g(x)))
)
(COMMENT R4 in Example 2 of \cite{GOO98})
(COMMENT revision of cops 28.trs, which is commented 
as Example 2 of \cite{GOO98} but incorrect.)