Analysis of information sources in references of the Wikipedia article "Перші сім Вселенських соборів" in Ukrainian language version.
... Tarasius ... skilfully put forward the project of an Ecumenical Council which should restore peace and unity to the Christian world. The Empress [...] summoned the prelates of Christendom to Constantinople for the spring of 786. ... Finally the Council was convoked at Nicaea in Bithynia; it was opened in the presence of the papal legates on 24 September 787. This was the seventh Ecumenical Council.