        Call Approximation</a>
              </li>
            </ul>
          </li>
        </ul>
      </li>
      <li>
        <a href="#ProcedureReturn">7. 
        Procedure Return (Response)</a>
        <ul class="toc">
          <li>
            <a href="#ResponseStatusCodes">7.1. 
        HTTP Status Code Requirements</a>
          </li>
          <li>
            <a href="#ResponseHeaders">7.2. HTTP Header Requirements</a>
          </li>
          <li>
            <a href="#Head25">7.3. 
        P