NO Problem: a(x1) -> x1 a(b(x1)) -> x1 a(b(x1)) -> b(c(a(a(x1)))) c(c(x1)) -> b(x1) Proof: String Reversal Processor: a(x1) -> x1 b(a(x1)) -> x1 b(a(x1)) -> a(a(c(b(x1)))) c(c(x1)) -> b(x1) Unfolding Processor: loop length: 10 terms: b(a(a(a(a(c(a(a(x73580)))))))) a(a(c(b(a(a(a(c(a(a(x73580)))))))))) a(a(c(a(a(c(b(a(a(c(a(a(x73580)))))))))))) a(a(c(a(c(b(a(a(c(a(a(x73580))))))))))) a(a(c(c(b(a(a(c(a(a(x73580)))))))))) a(a(b(b(a(a(c(a(a(x73580))))))))) a(a(b(a(a(c(b(a(c(a(a(x73580))))))))))) a(a(b(a(a(c(c(a(a(x73580))))))))) a(a(b(a(a(b(a(a(x73580)))))))) a(a(b(a(a(a(a(c(b(a(x73580)))))))))) context: a(a([])) substitution: x73580 -> c(b(x73580)) Qed