CCITT high level language (CHILL) : international standard ISO/IEC 9496: recommendation Z.200/International Telecommunication Union
Man-machine language (MML) : recommendation Z.301 - Z.341/International Telecommunication Union
The protection of telecommunication lines and equipment against lightning discharges : (Chapters 9 and 10) / International Telecommunication Union
Handbook earthing and bonding / International Telecommunication Union