Annex F.2 to recommendation Z.100 : SDL formal definition: static semantics/International Telecommunication Union
Annex F.3 to recommendation Z.100 : SDL formal definition: dynamic semantics/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 6, 7 and 8) / International Telecommunication Union