Approximation of the Beta function

The asymptotic expansion for the F score, equation 48, requires the value of $\log(\beta(\frac{D_2}{2},\frac{D_1}{2}))$. A similar approximation to that used in the last section for the T score has not been found. Hence, equation 7 is used, but by using an implementation of $\log(\Gamma(x))$ that does not calculate $\Gamma(x)$ itself. This is necessary since values of $\Gamma(x)$ will be so large as to cause computer overflow.