NO Problem: a(x1) -> b(x1) a(c(x1)) -> x1 c(b(b(x1))) -> a(a(a(c(c(x1))))) Proof: String Reversal Processor: a(x1) -> b(x1) c(a(x1)) -> x1 b(b(c(x1))) -> c(c(a(a(a(x1))))) Unfolding Processor: loop length: 12 terms: a(b(c(b(c(c(x198979)))))) b(b(c(b(c(c(x198979)))))) c(c(a(a(a(b(c(c(x198979)))))))) c(c(b(a(a(b(c(c(x198979)))))))) c(c(b(b(a(b(c(c(x198979)))))))) c(c(b(b(b(b(c(c(x198979)))))))) c(c(b(b(c(c(a(a(a(c(x198979)))))))))) c(c(c(c(a(a(a(c(a(a(a(c(x198979)))))))))))) c(c(c(c(a(a(b(c(a(a(a(c(x198979)))))))))))) c(c(c(c(a(a(b(c(b(a(a(c(x198979)))))))))))) c(c(c(c(a(a(b(c(b(b(a(c(x198979)))))))))))) c(c(c(c(a(a(b(c(b(b(b(c(x198979)))))))))))) context: c(c(c(c(a([]))))) substitution: x198979 -> a(a(a(x198979))) Qed