The Truth About ‘Breathing Into Your Stomach’

Read About Breathing and Support for Singing

If in Doubt, Breathe Out! by Ron Morris & Linda Hutchison — describes respiratory anatomy and physiology, and critiques common myths in breath management for voice.
Available: https://www.comptonpublishing.co.uk/if-in-doubt-breathe-out.php

Read About How the Voice Works:

Principles of Voice Production by Ingo R. Titze — foundational text on biomechanics of the human voice, including diaphragm, lung and rib‑cage function.
Available: https://books.google.com.au/books/about/Principles_of_Voice_Production.html?id=ytAeAQAAMAAJ&redir_esc=y

Read About the Mechanics of Voice Production:

“Mechanics of human voice production and control” (PMC article) — offers a review of anatomy/physiology in voice and clarifies some misconceptions.
Available: https://pmc.ncbi.nlm.nih.gov/articles/PMC5412481/?