There's a full description of the development of the J-9 and J-13 with severals configurations under test / consideration, which were - at least to me - formerly unknown. The most interesting part is the J-9VI-2 a twin engined version of the J-9 we already knew which was under development until the 80s.
I'm currently in the last steps to finish the text for a future IAPR-article and JP is once again drawing the profiles ! ;D
So hopefully some of You would be interested,