    Thomas Patterson,<br>
          The Optimal Addition of Points to Quadrature Formulae,<br>
          Mathematics of Computation,<br>
          Volume 22, Number 104, October 1968, pages 847-856.
        </li>
        <li>
          Knut Petras,<br>
          Smolyak Cubature of Given Polynomial Degree with Few Nodes
          for Increasing Dimension,<br>
          Numerische Mathematik,<br>
          Volume 93, Number 4, February 2003, pages 729-753.
        </li>
        <li>
          Sergey Smolyak,