Category for sites that are about the Bliss Bibliographic Classification System.

Category for sites the deal with or are about the Colon Classification System.

The Dewey Decimal System is used for classifying library materials. It was created by Melvil Dewey in the 1870s.

Category for sites dealing with the Library of Congress Subject Heading and classification schemes. This system is primarily used by academic libraries and large public libraries.

Category for sites that deal with subject specific classification systems for cataloging items in a library collection.

Category for sites dealing with the SuDocs classification system. This is the system used by government documents librarians in the United States of America.

The Universal Decimal Classification is an indexing and retrieval language in the form of a classification for the whole of recorded knowledge, in which subjects are symbolized by a code based on Arabic numerals. It was designed by the Belgian bibliographers Paul Otlet and Henry Lafontaine at the end of the 19th century, and has been improved and developed ever since.