Christopher Nolan Explains The Dark Knight

The Treatment - Christopher Nolan: The Dark Knight
https://www.kcrw.com/culture/shows/the-treatment/christopher-nolan-the-dark-knight
Collider - David Goyer and Jonathan Nolan Interview – THE DARK KNIGHT
http://collider.com/david-goyer-and-jonathan-nolan-interview-the-dark-knight/
The Art and Making of the Dark Knight Trilogy (print)
https://www.amazon.com/Art-Making-Dark-Knight-Trilogy/dp/1419703692
The Making Of Heath Ledger's Joker
https://www.empireonline.com/movies/features/heath-ledger-joker/