et al. & Roland Bielmeier 
Verbs [PDF ebook] 

This landmark dictionary serves as a basis for historical-comparative research on Tibetan. Conceptualized empirically and etymologically, it builds on extensive data from the Tibetan dialects and establishes the relationship to Written Tibetan. It reflects historical sound change and semantic change in all of linguistic Tibet. Based on historical sound change and geographical distribution, the dictionary applies a new classification of the Tibetan dialects.