== External links ==
* [http://www.geocities.com/trvalentine/orthodox/dragas_eighth.html The Eighth Ecumenical Council: Constantinople IV (879/880) and the Condemnation of the ''Filioque'' Addition and Doctrine] by Protopresbyter [[George Dragas|George Dion Dragas]]
* [http://www.geocities.com/trvalentine/orthodox/8-9synods.html The Eighth and Ninth Ecumenical Councils]