(VAR x y z)
(RULES
  +(x,0)  -> x
  +(x,s(y))  -> s(+(x,y))
  *(x,0) -> 0
  *(x,s(y)) -> +(*(x,y),x)
  +(+(x,y),z) -> +(x,+(y,z))
  +(x,y) -> +(y,x)
)
(COMMENT from the collection of \cite{AT2012})