MLA

Nowell, Frank H., 1864-1950. Flathead family - Montana. Early 1900's. https://collections.library.yale.edu/catalog/2011210.

APA, 6th edition

Nowell, Frank H., 1864-1950. (Early 1900's)[Flathead family - Montana]. https://collections.library.yale.edu/catalog/2011210.