lass="highlight">
  <p>
    <strong>Lemma 12.1.</strong>
    <em>
      Suppose that \( L/K \) is a field extension, \( M \) is an
      intermediate field, and \( \tau \) is a \( K \)-automorphism of \(
      L \).  Then \( \tau M^* \tau^{-1} = \tau(M)^{*} \).
    </em>
  </p>
</div>
<p>
  The notation \( M^* \) denotes the group of all
  \( M \)-automorphisms of \( L \) with composition as the group
  operation.  Note that Stewart writes \( \tau(M)^{*} = \tau M^*
  \tau^{-1} \) while stating the lemma but