William Mortensen: The Command to Look: A formula for picture success, 1937

William Mortensen: Mortensen on the Negative

Ansel Adams: The Negative

It is surprising how similar results these two completely different approaches give. And that, I think, may well be the reason for the hostility.

I'll add one more I have learned a lot from:

Willi Beutler: Meine Dunkelkammer-Praxis