Gunther, D., Recommendation on Quality Assurance and Selection of resources for the ETB network Archived September 27, 2007, at the Wayback Machine, European Treasury Browser, P. 48., 2002, retrieved 3/7/07.
Gunther, D., Recommendation on Quality Assurance and Selection of resources for the ETB network Архивировано 27 сентября 2007 года., European Treasury Browser, P. 48., 2002, retrieved 3/7/07.