Ulysse: http://www.ulysse.fr/
UMTS (Universal Mobile Telecommunications Service) Forum: http://www.umts-forum.org/
UNDL (universal networking digital language) Foundation: http://www.undl.org/
UNESCO (Organisation des Nations Unies pour l’éducation, la science et la culture): http://portal.unesco.org/fr/
UNESCO Copyright: http://www.unesco.org/culture/copyright/
UNESCO Documents and Publications: http://unesdoc.unesco.org/ulis/
UNESCO Libraries Portal: http://www.unesco.org/webworld/portal_bib/
Unicode: http://www.unicode.org/
Unicode Consortium: http://www.unicode.org/consortium/
UNIMARC (universal machine readable cataloguing): http://www.ifla.org/VI/3/p1996-1/concise.htm