The change cannot be regarded as a subsequent terminological regression caused by the fact that Yankton-Yanktonai people lived together with the Santee in the same reserves. The oldest texts that document the Sioux dialects are devoid of historic references to Nakota. Ullrich notes particularly that John P. Williamson's "English-Dakota Dictionary" (1902) lists Dakota as the proper name for the Dakota people, but does not mention Nakota. Still, Williamson had worked extensively with the Yankton and frequently included in his dictionary Yankton variants for Santee entries. Moreover, Ullrich notes that the Yankton scholar Ella Cara Deloria (born in 1888) was among the first to point out "the fallacy of designating the Yankton-Yanktonai groups as Nakota.".