ISO 3297:2017 defines and promotes the use of a standard code (ISSN) for the unique identification of serials and other continuing resources. Each International Standard Serial Number (ISSN) is a unique identifier for a specific serial or other continuing resource in a defined medium. ISO 3297:2017 also describes a mechanism, the "linking ISSN (ISSN-L)", that provides for collocation or linking among the different media versions of the same continuing resource. ISSN are applicable to serials and to other continuing resources, whether past, present or to be published or produced in the foreseeable future, whatever the medium of publication or production. Individual monographs, sound and video recordings, printed music publications, audiovisual works and musical works have their own numbering systems and are not specifically mentioned in ISO 3297:2017. Such items may carry an ISSN in addition to their own standard numbers when they are part of a continuing resource. More detailed operational guidance is provided in the ISSN Manual available from the Registration Authority for ISO 3297:2017 (see Clause 11).