The ISSN number, along with the key title, is the basic element for identification of the serial publications. It represents the integral part of the BIBLID for identification of supplements (articles) of serial publications and EAN (BAR) code for optical recognition of the serial publications. It is printed on the upper right corner of the cover and title page of the publication. It has been allotted by the ISSN Centre of Serbia and Montenegro (since January 2004, the Centre is within the National Library of Serbia). To obtain the ISSN number, the Publishers have to contact this Centre (by telephone, fax or email) with the elementary datas of the Periodical.