T. W. Rhys Davids 
Buddhism Being a Sketch of the Life and Teachings of Gautama [PDF ebook] 

Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. Keith Johnston, Physical Atlas, ‘ ed. 1856, estimates thesi states tributary to China to contain inhabitants. So far as I can gather, this seems to be too much. The total of the above estimate is 20.