NO Problem: a(x1) -> x1 a(b(x1)) -> b(c(b(a(a(x1))))) b(x1) -> a(x1) c(c(x1)) -> x1 Proof: String Reversal Processor: a(x1) -> x1 b(a(x1)) -> a(a(b(c(b(x1))))) b(x1) -> a(x1) c(c(x1)) -> x1 Unfolding Processor: loop length: 9 terms: b(a(a(a(x92236)))) a(a(b(c(b(a(a(x92236))))))) a(a(b(c(a(a(b(c(b(a(x92236)))))))))) a(a(b(c(a(b(c(b(a(x92236))))))))) a(a(b(c(b(c(b(a(x92236)))))))) a(a(b(c(a(c(b(a(x92236)))))))) a(a(b(c(c(b(a(x92236))))))) a(a(b(b(a(x92236))))) a(a(b(a(a(b(c(b(x92236)))))))) context: a(a([])) substitution: x92236 -> c(b(x92236)) Qed