I'm looking for a good, modern reference for the diffusion approximation to the radiative transport problem. I'm aware of the text of Dautray and Lions, as well as the monograph by Bensoussan, Lions, and Papanicolaou, but these are a bit dated and difficult to read. My motivation is studying the (in)stability of the inverse radiative transport problem. More specifically, I am hoping to better understand the estimate in pages 8-10 in the following paper of H.K. Zhao.
