Would anybody know of a video lecture course in which Polyakov's non-critical string path integral
$$Z = \int D [\psi(\xi)]\, \, \exp \left\{ \frac{D-26}{48 \pi}\int_{\xi}\left(\tfrac{1}{2}(\partial_\mu \psi)^2+\mu^2e^{\psi}\right) \right\}$$
is fully derived? Hopefully it's part of one of the many string theory courses online, perhaps someone has come across it.
The result is very briefly sketched at the very end of this video and continued into the beginning of this one, it's so inspiring I'd love to see this fully developed.