A reference work is a work such as a book or periodical (or its electronic equivalent) to which one can refer for information. The information is intended to be found quickly when needed. Reference works are usually referred to for particular pieces of information, rather than read beginning to end. The writing style used in these works is informative; the authors avoid use of the first person, and emphasize facts. Many reference works are compiled by a team of contributors whose work is coordinated by one or more editors rather than by an individual author. Indices are commonly provided in many types of reference work. Updated editions are usually published as needed, in some cases annually (e.g. Whitaker's Almanack, Who's Who). Reference works include dictionaries, encyclopedias, almanacs, atlases, bibliographies, biographical sources, catalogs such as library catalogs and art catalogs, concordances, directories such as business directories and telephone directories, discographies, filmographies, glossaries, handbooks, indices such as bibliographic indices and citation indices, manuals, research guides, thesauruses, and yearbooks. Many reference works are available in electronic form and can be obtained as reference software, CD-ROMs, DVDs, or online through the Internet.
A reference work is useful to its users if they attribute some degree of trust.