where s n is the n-th root of the Legendre polynomial of degree N l , and w n is the corresponding quadrature weight. Fig. demonstrates that {s n } covers the interval [-1, +1] mostly uniformly and the corresponding weights become similar in magnitude as N l increases. Besides, since ζ < 5 (Fig. ) and with s n confined within [-1, +1], e -ζ 2 s 2 n in Eq. 10 does not vary tremendously. These properties make the Gauss-Legendre quadrature more advantageous than the Gauss-Hermite quadrature for numerical implementation.