          sets the exact integral for problem 19.
        </li>
        <li>
          <a href = "p19_f.m">p19_f.m</a>, 
          evaluates the integrand for problem 19.
        </li>
        <li>
          <a href = "p19_i4.m">p19_i4.m</a>, 
          sets or gets I4 parameters for problem 19.
        </li>
        <li>
          <a href = "p19_lim.m">p19_lim.m</a>, 
          returns the integration limits for problem 19.
        </li>
        <li>
          <a href = "p19_name.m">p19_name.m</a>, 
      