YES 1: +(+(x1,x2),x3) -> +(x1,+(x2,x3)) 2: +(x1,x2) -> +(x2,x1) 3: *(+(x1,x2),x3) -> +(*(x1,x3),*(x2,x3)) @Jouannaud and Kirchner's criterion --- R 1: +(+(x1,x2),x3) -> +(x1,+(x2,x3)) 2: +(x1,x2) -> +(x2,x1) 3: *(+(x1,x2),x3) -> +(*(x1,x3),*(x2,x3)) --- S 1: +(+(x1,x2),x3) -> +(x1,+(x2,x3)) 2: +(x1,x2) -> +(x2,x1) 3: *(+(x1,x2),x3) -> +(*(x1,x3),*(x2,x3))