$\displaystyle \partial_t \eta (t) = g(\eta(t),\varphi(t))$
$--a {\frac{1}{2}} @minus{}$ $--a@minus{} {\frac{1}{2}}$
$\displaystyle disp--laymath
f(x) = {1 \over \sigma \sqrt{2\pi}}e@sup{-{1 \over 2}\left({x-\mu \over \sigma}\right)^2}
$