Y. Y. Zhang, Y. Lei and A. P. Liao. (2007). Least-Squares Solutions of the Matrix Equation <em>A<sup>T</sup>XA=B</em> Over Bisymmetric Matrices and its Optimal Approximation.
            <i>Numerical Mathematics, a Journal of Chinese Universities</i>. <i>16</i> (3).
            215-225.
         doi: