NO Problem: a(x1) -> x1 a(b(x1)) -> a(a(c(b(b(a(x1)))))) b(x1) -> x1 c(c(x1)) -> x1 Proof: String Reversal Processor: a(x1) -> x1 b(a(x1)) -> a(b(b(c(a(a(x1)))))) b(x1) -> x1 c(c(x1)) -> x1 Unfolding Processor: loop length: 7 terms: b(a(c(a(x1210)))) a(b(b(c(a(a(c(a(x1210)))))))) a(b(b(c(a(c(a(x1210))))))) a(b(b(c(c(a(x1210)))))) a(b(b(a(x1210)))) a(b(a(b(b(c(a(a(x1210)))))))) a(b(a(b(c(a(a(x1210))))))) context: a([]) substitution: x1210 -> a(x1210) Qed