ADS
[1] Application Development System[2] Activity Data Sheet \{Luftfahrt\}
[3] Accurately Defined System
[4] Aitken Double Star catalogue - Katalog mit über 17000 Doppelsternen von Robert G. Aitken von 1932 (->"Penguin Dictionary of Astronomy")
[5] Astrophysics Data System (NASA/HAVARD)
[6] Automatic Distribution System
[7] Active Directory Service - proprietäres X.500 unter Windows NT (Microsoft, vergl. NDS)
[8] Advanced Digital System
[9] Audio Distribution System
[10] Auxilary Data System
[11] Dallas-Addison, TX, USA -internationale Fughafen-Kennung