(VAR x y z)
(RULES
  +(x,+(y,z)) -> +(+(x,y),z)
  +(+(x,y),z) -> +(x,+(y,z)) 
  +(x,y) -> + (y,x)
  +(s(x),y) -> +(x,s(y))
  +(x,s(y)) -> +(s(x),y)
  *(x,s(y)) -> +(x,*(x,y))
  *(s(x),y) -> +(*(x,y),y)
  *(x,y) -> *(y,x)
  sq(x) -> *(x,x)
  sq(s(x)) -> +(*(x,x),s(+(x,x)))
)
(COMMENT from Example 1 of \cite{OO03})