NO Problem: a(x1) -> x1 a(b(x1)) -> b(a(c(b(a(a(x1)))))) c(b(c(x1))) -> x1 Proof: String Reversal Processor: a(x1) -> x1 b(a(x1)) -> a(a(b(c(a(b(x1)))))) c(b(c(x1))) -> x1 Unfolding Processor: loop length: 7 terms: b(a(a(a(x4731)))) a(a(b(c(a(b(a(a(x4731)))))))) a(a(b(c(b(a(a(x4731))))))) a(a(b(c(a(a(b(c(a(b(a(x4731))))))))))) a(a(b(c(a(b(c(a(b(a(x4731)))))))))) a(a(b(c(b(c(a(b(a(x4731))))))))) a(a(b(a(b(a(x4731)))))) context: a(a([])) substitution: x4731 -> b(c(a(b(x4731)))) Qed