"Morpho - Anatomy for Artists" by Michel Lauricella."Relationship between the arm and torso." This is the main book I've been going through a little more on than off for the past year, thanks to COVID lock downs freeing up a bunch of time among the madness.This is as big a dent as I've put in it. Not even half of it, but it's still going.Here's some of the "studies" I've done from it to the best of my ability, for reference.