     over the interior of a tetrahedron in 3D.
    </p>

    <p>
      Newton-Cotes rules have the characteristic that the abscissas
      are equally spaced.  For a tetrahedron, this refers to spacing
      in the unit reference tetrahedron, or in the barycentric coordinate
      system.  These rules may be mapped to an arbitrary tetrahedron,
      and will still be valid.
    </p>

    <p>
      The rules are said to be "open" when they do not include points on
      the boundary of the tetrahedron.
    <