A Buddha Within: The Tathagatagarbha Sutra: The Earliest Exposition of the Buddha-nature teaching in India.

Buddha nature which is an essence or nature that exists in all sentient beings allows that being to become Enlightened which all the obstacles to buddha nature have been cleared away.

In this book Michael Zimmerman gives an exhaustive account of how the concept of buddha nature arose in India principally through this sutra. This exhaustive study of over 400 pages includes the translation of this sutra into Tibetan and also Chinese. Each of these Buddhist Countries at the time translated this Sanskrit sutra into their respective languages allow  modern scholars to see the differences and similaries of their interpretation of this valuable sutra.