Sources

Here you find a list of my sources, as complete as possible.

One thing that is always helpful if you search for knowledge about Don's drawing techniques is a simple Google image search for original drawings*, since there are some high resolution images where you can e.g. see that some lines are darker than others pretty well - this can be pretty helpful to check where Don used which pen. If you want to know more about that, go to the pen page.

This image also helped me a lot:

(*but a real insider's tip for high resolution original images are auction sites like Heritage Auctions - no advertisement, just a recommendation. Not sponsored.)