Lists of words and/or phrases that are used to index and/or retrieve content, and that may include cross-references. For lists of words and their synonyms and often their antonyms see Thesauri (Dictionaries).
Books intended for travelers that provide information about a particular geographical location, often including descriptions of lodgings, restaurants, and places of interest.
Works consisting wholly or chiefly of systematic guides to the content of resources, usually presented as alphabetical lists of names, places, subjects, etc., with references to their locations in the resources.