Under Southern Athabaskans, includes (p. 308) Kwalioqwa, Tlatskanai, Umkwa.
"Indian Linguistic Families Of America, North Of Mexico" by John Wesley Powell
The Athabaskans of Hudson's Bay were on about the same level of savagery.
"The Discovery of America Vol. 1 (of 2)" by John Fiske
All the Athabaskan languages or dialects are mutually intelligible.
"The Ethnology of the British Colonies and Dependencies" by Robert Gordon Latham
Author of a number of primers in the Athabaskan and Algonquian languages, as well as in Eskimo.
"The Makers of Canada: Index and Dictionary of Canadian History" by Various
Contemplating the distribution of the tribes belonging to the Athabaskan stock in three divisions, viz.
"Encyclopaedia Britannica, 11th Edition, Volume 14, Slice 4" by Various