Currently, we store MARC21 690 in the Subject index, but perhaps we should also store it in a Local-Subject index. (I'm not really sure why, but it's something that we've done locally for a while.) We might also want to include 691, 695, 696, 697, 698, 699 in both the Subject and Local-Subject indexes, as these are also valid subject fields. It looks like Robin has created bug 10308 to deal with adding authority linking.