YES ---- CR(R) ---- [Knuth and Bendix, 1970] R: f(g(x,a(),b())) -> x g(f(h(c(),d())),x,y) -> h(k1(x),k2(y)) k1(a()) -> c() k2(b()) -> d() f(h(k1(a()),k2(b()))) -> f(h(c(),d())) f(h(c(),k2(b()))) -> f(h(c(),d())) f(h(k1(a()),d())) -> f(h(c(),d())) CP(R): f(h(k1(a()),k2(b()))) -> f(h(c(),d())) f(h(c(),k2(b()))) -> f(h(c(),d())) f(h(c(),d())) -> f(h(c(),d())) f(h(k1(a()),d())) -> f(h(c(),d())) f(h(c(),d())) -> f(h(c(),d()))