*Juha Hakala, [http://www.persid.org/downloads/PI-intro-2010-09-22.pdf Juha Hakala, "Persistent identifiers – an overview."] Posted to Technology Watch Report (TWR): Standards in Metadata and Interoperability, 13 Oct 2010.
*[Hans-Werner Hilse and Jochen Kothe, <!-- https://web.archive.org/web/20161203115538/http://nbn-resolving.de/urn:nbn:de:gbv:7-isbn-90-6984-508-3-8/ Hans-Werner(ironically, Hilsethis and"identifier" Jochenfailed Kothe,to persist -->[http://webdoc.sub.gwdg.de/edoc/ah/2006/hilse_kothe/urn:nbn:de:gbv:7-isbn-90-6984-508-3-8.pdf ''Implementing persistent identifiers: overview of concepts, guidelines and recommendations.''] London / Amsterdam: [[Consortium of European Research Libraries]] and European Commission on Preservation and Access, 2006. {{ISBN|90-6984-508-3}}.
