Does anyone have a citation or site one can go to in order to learn what Churchill's claims actually are as to his Indian status?

I know I just read he claims 1/16 Indian blood. That should mean (if my arithmetic is correct) that he had a great-grandparent who was full Indian. Does he anywhere substantiate that, or try to? "My great-grandfather Joe Jones was Kiowa, lived from 18__ until about 19__, and died in Yankton, South Dakota," or something like that?

Or does he just make the bald claim?

Dave Oesterreich