Use in URNs
An ISSN can be encoded as a Uniform Resource Name (URN) by prefixing it with "urn:ISSN:". For example Rail could be referred to as "urn:ISSN:1534-0481". URN namespaces are case-sensitive, and the ISSN namespace is all caps. If the checksum digit is "X" then it is always encoded in uppercase in a URN.
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