Helpful Links: (For informational purposes only, I don't endorse any of these links.)
- Pranayama: a Sanskrit word meaning "extension of the prāṇ or breath" or, "extension of the life force".
- The Science of Breath (Book) by Yogi Ramacharaka. Considered by many to be the timeless authority on breath.
- Science of Breath (PDF) PDF form of Yogi Ramacharaka's classic.
- Science of Breath (html) Yogi Ramacharaka's text listed in html format.
- Art and Science of Breathing Informative site by Dr. Andrew Weil.
- The Hindu-Yogi Science Of Breath A free ebook from by William Walker Atkinson.
- The Science of Breath & the Philosophy of the Tatwas If you're really into it and want to go way out there, this is a publication from the Theosophical Society.
- ABC of Yoga Information on Pranayama and Yoga exercise.
- The Science of Pranayama Published by the Divine Life Society.
- PranayamaMac App Believe it or not you can even get an app from iTunes.