found: LCSH, Dec. 1, 2009:(hdg.: Index maps)
found: Wikipedia, Dec. 1, 2009:(index map: a type of finding aid that allow users find a set of maps covering their regions of interest along with the name or number of the relevant map sheet. An index maps provides geospatial representation on either a sheet of paper or a computer screen)
found: Glossary of the mapping sciences, 1994:index map (a map showing where to find collections of related data such as other rmaps, aerial photographs, statistical data, or descriptions of terrain. Also called a key map. Index maps may be used to show references ot the origin, place of deposit, or filing or other identifying characteristics of such data)
notfound: Glossary of mapping, charting, and geodetic terms, 1973.