---- CR(R) ---- [van Oostrom, RTA 2008]. R: +(s(x),y) -> s(+(x,y)) +(x,s(y)) -> s(+(x,y)) +(x,y) -> +(y,x) Label: [+(s(x),y) -> s(+(x,y))] = 1 [+(x,s(y)) -> s(+(x,y))] = 1 [+(x,y) -> +(y,x)] = 0