Ryåogen and Mount Hiei[: Japanese Tendai in the Tenth Century - Paul Groner - Google Books

https://books.google.de/books?id=B1eVBPvvFMgC

This work focuses on the transformation of the Tendai School from a small and impoverished group of monks in the early ninth century to its emergence as the most powerful and influential school in Japanese Buddhism in the last half of the tenth century.