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