Can the source be found and is it available?
In order to find the source, sufficient bibliographical information should be available. This includes the title, author, date of publication, edition and the publishing institution (publisher, authority, company, university).
The source should be accessible to erveryone. This means that it should be available in locations open to the public, such as bookshops, libraries, archives or via permanent internet links.
Please note: the retrievability of conference contributions, working papers and other unpublished materials is not always possible and must be checked carefully.