Cookbook:
Nourishing Traditions by Sally Fallon
pp. 181 (stocks and broths), and 181-211 (soups); besides the
recipes you’ll find plenty of food lore and excerpts from
long-forgotten books and articles on the importance of broth.
Book:
Restoring Your Digestive Health, Jordan Rubin and
Joseph Brasco; thorough discussion of what works and what
doesn’t with a detailed program that includes broth, see pp.99,
254-55, 328, etc.