:::Using what I have learned, I set up the Authority Control template for Agnes Martin, the artist honored in the Google doodle for 22 March. It worked! I found three index numbers to enter in the template, and then somehow many others were filled in, including BNF. For this person, 'data' went to a link quite full of information on her. I see this differs by person; the pattern of difference is not obvious, but at least it is not always a 404 error. Now I know to look for these on articles about persons, and see what I might learn clicking on those links.