Universal identifiers

An International Standard Serial Number (ISSN) is an eight-digit to uniquely identify a periodical publication (periodical), such as a magazine. The ISSN is especially helpful in distinguishing between serials with the same title. ISSNs are used in ordering, cataloging, interlibrary loans, and other practices in connection with serial literature.

A Smithsonian trinomial (formally the Smithsonian Institution Trinomial System, abbreviated SITS) is a unique identifier assigned to archaeological sites in many states in the United States. Trinomials are composed of a one or two digit coding for the state, typically two letters coding for the county or county-equivalent within the state, and one or more sequential digits representing the order in which the site was listed in that county. The Smithsonian Institution developed the site number system in the 1930s and 1940s, but it no longer maintains the system. Trinomials are now assigned by the individual states. The 48 states then in the union were assigned numbers in alphabetical order. Alaska was assigned number 49 and Hawaii was assigned number 50, after those states were admitted to the union. There is no Smithsonian trinomial number assigned for the District of Columbia or any United States territory.

The International Standard Book Number (ISBN) is a numeric commercial book identifier that is intended to be unique. Publishers purchase or receive ISBNs from an affiliate of the International ISBN Agency.

ResearcherID is an identifying system for scientific authors. The system was introduced in January 2008 by Thomson Reuters Corporation.

The Library Network of Western Switzerland (French: Réseau des bibliothèques de Suisse occidentale; RERO) was founded by several major libraries in 1985, in the French-speaking region of Romandy in western Switzerland. RERO is a syllabic abbreviation of "Réseau Romand" ("Romand Network").

In the United States, a Social Security number (SSN) is a nine-digit number issued to U.S. citizens, permanent residents, and temporary (working) residents under section 205(c)(2) of the Social Security Act, codified as 42 U.S.C. § 405(c)(2). The number is issued to an individual by the Social Security Administration, an independent agency of the United States government. Although the original purpose for the number was for the Social Security Administration to track individuals, the Social Security number has become a de facto national identification number for taxation and other purposes.

The Universal Product Code (UPC or UPC code) is a barcode symbology that is used worldwide for tracking trade items in stores.

CODEN – according to ASTM standard E250 – is a six-character, alphanumeric bibliographic code that provides concise, unique and unambiguous identification of the titles of periodicals and non-serial publications from all subject areas.

The Entertainment Identifier Registry, or EIDR, is a global unique identifier system for a broad array of audiovisual objects, including motion pictures, television, and radio programs. The identification system resolves an identifier to a metadata record that is associated with top-level titles, edits, DVDs, encodings, clips, and mashups. EIDR also provides identifiers for video service providers, such as broadcast and cable networks.