NO Problem: a(x1) -> x1 a(b(x1)) -> b(a(a(c(b(a(x1)))))) b(x1) -> x1 c(c(x1)) -> x1 Proof: String Reversal Processor: a(x1) -> x1 b(a(x1)) -> a(b(c(a(a(b(x1)))))) b(x1) -> x1 c(c(x1)) -> x1 Unfolding Processor: loop length: 7 terms: b(a(a(x14973))) a(b(c(a(a(b(a(x14973))))))) a(b(c(a(b(a(x14973)))))) a(b(c(b(a(x14973))))) a(b(c(a(b(c(a(a(b(x14973))))))))) a(b(c(b(c(a(a(b(x14973)))))))) a(b(c(c(a(a(b(x14973))))))) context: a([]) substitution: x14973 -> b(x14973) Qed