 Theorem 3.8: There are c.e. sets \(A\) and \(B\) such that \(A \nleq_T B\) and \(B \nleq_T A\). Thus if \(\mathbf{a} = \textrm{deg}_T(A)\) and \(\mathbf{b} = \textrm{deg}_T(B)\), then \(\mathbf{a} \nleq_T \mathbf{b}\) and \(\mathbf{b} \nleq_T \mathbf{a}\) and hence also \(\mathbf{0} &lt;_T \mathbf{a} &lt;_T \mathbf{0}'\) and \(\mathbf{0} &lt;_T \mathbf{b} &lt; _T\mathbf{0}'\).