Terms for these must be ANDed with other terms to limit the size of the result set. See the table provided for each restrictor to determine valid terms and their associated meaning. The Extended Author search can also be a phrase search only. The suggested strategy in searching for records that contain those subheadings is to and those terms together. Restrictor codes were created for the most common languages so that quicker results could be obtained for a search.
Language is both an index and a restrictor.
The Keyword index for WorldCat uses attribute number 1016. This is a field useful to map catalogers. The most distinict term in the string is the most useful to search on. Secondary Document Type is a search index offered for users who want to have a definitive search for all records of a document type. The US MARC record allows multiple document types in the 006 fields.