S.R. Ramsey writes (1979: 162): "The patterning of tone marks in Old Kyoto texts divides the vocabulary into virtually the same classes as those arrived at by comparing the accent distinctions found in the modern dialects. This means that the Old Kyoto dialect had a pitch system similar to that of proto-Japanese. The standard language of the Heian period may not actually be the ancestor of all the dialects of Japan, but at least as far as the accent system is concerned, it is close enough to the proto system to be used as a working model. The significance of this fact is important: It means that each of the dialects included in the comparison has as much to tell, at least potentially, as any other dialect about Old Kyoto accent."