In manual systems, whether in the form of a card catalog or a vertical file of pictures, only the first word in the subject heading string can be searched. Alternative indexing techniques may be needed to enable researchers to retrieve an image by its various aspects and to find it in close proximity to related images. These techniques might include indexing separately for topical and geographic aspects of the image and double indexing images at more than one level of a hierarchy of terms. For example, a beach scene in Santa Monica, California, could be indexed under Santa Monica (Calif.); California; and Beaches--California--Santa Monica. Automated systems that feature keyword searching would require only the last heading in order to make all three concepts fully accessible.
Institutions may also find it useful to subdivide selected broad terms (BT) by their narrower terms (NT) in order to collocate related materials in browsing files, as well as to subdivide generic TGM I terms by proper names rather than double indexing in the manner described in Section II.D. These techniques are not authorized for use in MARC records, but may be used in local card catalogs and vertical files.
Example: Animals NT Tapirs becomes Animals--Tapirs Example: Industry NT Tobacco industry becomes Industry--Tobacco industry Example: Fraternal organizations becomes Fraternal organizations--Knights Templar (Masonic order) Example: Religious groups becomes Religious groups--Buddhists
If this technique is used, it may be helpful to searchers who begin by looking under specific terms if cross-references are supplied to point them to the broader topic under which they should search.