Nonetheless, by the end of Pagan period, the process of Burmanization, which would continue into the 19th century, and eventually blanket the entire lowlands, was still in an early stage. The first extant Burmese language reference to "Burmans" appeared only in 1190, and the first reference to Upper Burma as "the land of the Burmans" ("Myanma pyay") in 1235. The notion of ethnicity continued to be highly fluid, and closely tied to political power. While the rise of Ava ensured the continued spread of Burman ethnicity in post-Pagan Upper Burma, the similar emergence of non-Burmese speaking kingdoms elsewhere helped develop ethnic consciousness closely tied to respective ruling classes in Lower Burma, Shan states and Arakan. For example, according to Lieberman and Aung-Thwin, "the very notion of Mons as a coherent ethnicity may have emerged only in the 14th and 15th centuries after the collapse of Upper Burman hegemony".