NO Problem: a(x1) -> x1 a(x1) -> b(x1) b(b(c(x1))) -> a(c(c(c(a(b(x1)))))) Proof: String Reversal Processor: a(x1) -> x1 a(x1) -> b(x1) c(b(b(x1))) -> b(a(c(c(c(a(x1)))))) Unfolding Processor: loop length: 11 terms: c(b(b(b(b(x161959))))) b(a(c(c(c(a(b(b(x161959)))))))) b(a(c(c(c(b(b(b(x161959)))))))) b(a(c(c(b(a(c(c(c(a(b(x161959))))))))))) b(a(c(c(b(b(c(c(c(a(b(x161959))))))))))) b(a(c(c(b(b(c(c(c(b(b(x161959))))))))))) b(a(c(c(b(b(c(c(b(a(c(c(c(a(x161959)))))))))))))) b(a(c(c(b(b(c(c(b(b(c(c(c(a(x161959)))))))))))))) b(a(c(c(b(b(c(b(a(c(c(c(a(c(c(c(a(x161959))))))))))))))))) b(a(c(c(b(b(c(b(b(c(c(c(a(c(c(c(a(x161959))))))))))))))))) b(a(c(c(b(b(b(a(c(c(c(a(c(c(c(a(c(c(c(a(x161959)))))))))))))))))))) context: b(a(c([]))) substitution: x161959 -> c(c(c(a(c(c(c(a(c(c(c(a(x161959)))))))))))) Qed