formula

$la\left(\hat{\bf{a}}, \hat{\sigma}^2\right)&=&-\frac{1}{2}\left\{n\ln(2\pi \hat{\sigma}^2)+\frac{n\sigma^2_0}{\hat{\sigma}^2}+\frac{\displaystyle\sum_{i=1}^n(q(x_i)-\hat{p}(x_i))^2}{\sigma^2}\right\}$