Integrated Services Digital Network (ISDN) - Telephony 7 kHz teleservice - Functional capabilities and information flows; English version ETS 300265:1994
Integrated Services Digital Network (ISDN) - Telephony 7 kHz, videotelephony, audiographic conference and videoconference teleservices - Digital Subscriber Signalling System No. one (DSS1) protocol - Part 1: Protocol specification