James L. Harner, Literary Research Guide — Serial Bibliographies… (2017)
“ Despite the dramatic increase in accessibility to the post-1980 listings, a search of the printed subject indexes or online file must sometimes be supplemented by a reading of appropriate sections in the classified volumes. Although the number of index terms has grown steadily each year, many broad studies can be described in only the most general terms, and some publications, lacking a thesis or any discernible focus, cannot be given any descriptors. Subject indexing, at its best, is an imperfect art. ”
