What is an ISSN?
An ISSN, or International Standard Serial Number, is a unique eight digit number assigned to each journal title - they are very useful if the same title is shared by more than one journal. For example, two journals are called 'Economist' - one is from the Netherlands (ISSN: 1572-9982), one is from London, England (ISSN: 0013-0613).
You can find the ISSN of a journal using Ulrich's Periodical Directory.
Ordinarly, you do not need an ISSN to locate a journal in the library.
For more information got to the ISSN International Centre.