l_d1_o2_w.txt">
          gl_d1_o2_w.txt</a>,
          the weights of a 1D Clenshaw Curtis rule of order 2.
        </li>
        <li>
          <a href = "gl_d1_o2_r.txt">
          gl_d1_o2_r.txt</a>,
          defines the range of the region.
        </li>
      </ul>
    </p>

    <p>
      We give the command
      <blockquote>
        <b>product_rule</b> factors.txt
      </blockquote>
      <ul>
        <li>
          <a href = "factors.txt">
          factors.txt</a>,
          a file containing th