Endiel 91 : contribuição do CET
The 1990 world satellite annual : the official supplement of the world satellite almanac / Mark Long
Eurodata Foundation Yearbook 1988-89 / Eurodata Foundation
Eurodata Foundation Voicebook : April 88 - March 89 / Eurodata Foundation
Termes de radiocommunications : (Glos/80/81) Septembre 1980 / Union International des Telecommunications
British standard glossary of terms used in telecommunication / British Standards Institution