Within a citation (such as a <mixed-citation> or an <element-citation>), an ISSN designated by an ISSN Centre to group together the different media versions of a standards document. Since a single ISSN-L is assigned no matter how many media formats of a work there are, the ISSN-L can be used to link among the different media versions of the standards document or continuing resource, for example, both the printed and online versions of the same standards document.