The four tools traditionally used in libraries are:
Card catalog: A system of organizing and locating books and other materials using a set of cards, typically arranged in alphabetical order by author, title, or subject.
Bibliography: A list of books and other materials that have been published on a particular subject, often arranged by author, title, or subject.
Index: A list of specific terms, topics, or names, along with references to the pages or sections of a book or other publication where they can be found.
Reference works: Encyclopedias, dictionaries, atlases, and other specialized resources that provide information on a wide range of subjects.