NO Problem: a(x1) -> x1 a(b(x1)) -> b(a(a(c(a(a(x1)))))) c(c(x1)) -> b(x1) Proof: String Reversal Processor: a(x1) -> x1 b(a(x1)) -> a(a(c(a(a(b(x1)))))) c(c(x1)) -> b(x1) Unfolding Processor: loop length: 7 terms: b(a(a(x5241))) a(a(c(a(a(b(a(x5241))))))) a(a(c(a(b(a(x5241)))))) a(a(c(b(a(x5241))))) a(a(c(a(a(c(a(a(b(x5241))))))))) a(a(c(a(c(a(a(b(x5241)))))))) a(a(c(c(a(a(b(x5241))))))) context: a(a([])) substitution: x5241 -> b(x5241) Qed