Terminal equipment and protocols for telematic services : recommendations T.431 - T.564 / International Telecommunication Union
Data communication over the telephone network : series V recommendations / International Telecommunication Union
Data communication networks : transmission, signalling and switching, network aspects, maintenance and administrative arrangements: recommendations X.40 - X.181 / International Telecommunication Union
Data communication networks : open systems interconnection (OSI) model and notation, service definition: recommendations X.200 - X.219 /International Telecommunication Union