Data communication networks : interworking between networks, mobile data transmission systems, internetwork management: recommendations X.300 - X.370 /International Telecommunication Union
Data communication networks : message handling systems: recommendations X.400 - X.420 /International Telecommunication Union
Functional specification and description language (SDL) : criteria for using formal description techniques (FDTs): recommendation Z.100 and annexes A, B, C and E, recommendation Z.110 / International Telecommunications Union
Annex D to recommendation Z.100 SDL user guidelines/International Telecommunication Union