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