The Ashtanga Yoga of the Yoga Upanishads
HINDUISM
The Yoga of the Yoga Upanishads is fundamentally different from many other types of Yoga such as Hatha Yoga, Raja Yoga, Gnana Yoga, Bhakti Yoga, Kriya Yoga, etc. though there may be some common elements.
This book by Colonel Ramesh Sharma Alwar (Retd) provides a detailed explanation of Ashtanga Yoga and differentiates it from many other types of Yogas.