International Standard Book Numbers (ISBNs)
An ISBN is a 13-digit code which identifies one title or edition of a title from one specific publisher and is unique to that title or edition.
ISBNs for British and Irish publishers are issued (for a charge) by the UK International Standard Book Numbering Agency.
International Standard Serial Numbers (ISSNs)
An ISSN is an 8-digit code which identifies a journal or other serial publication, i.e., a publication issued in successive parts, having a common title, and intended to be continued indefinitely.
ISSNs in Ireland are issued by the Irish ISSN Centre in the National Library of Ireland.
ISSNs in the United Kingdom are issued by the ISSN UK Centre in the British Library.