Data communication networks : directory: recommendations X.500 - X.521/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 F.1 to recommendation Z.100 : SDL formal definition: introduction/International Telecommunication Union
Annex F.2 to recommendation Z.100 : SDL formal definition: static semantics/International Telecommunication Union