YES Problem: a(x1) -> b(x1) a(b(x1)) -> b(c(a(x1))) b(x1) -> c(x1) c(b(x1)) -> a(x1) Proof: KBO Processor: weight function: w0 = 1 w(b) = w(a) = 1 w(c) = 0 precedence: c > a > b problem: Qed