http://www.newadvent.org/cathen/06073a.htm
"In 796 the Patriarch of Aquileia justified and adopted the same addition at the Synod of Friaul, and in 809 the Council of Aachen appears to have approved of it. The decrees of this last council were examined by Pope Leo III, who approved of the doctrine conveyed by the Filioque, but gave the advice to omit the expression in the Creed."
"In 796 the Patriarch of Aquileia justified and adopted the same addition at the Synod of Friaul, and in 809 the Council of Aachen appears to have approved of it. The decrees of this last council were examined by Pope Leo III, who approved of the doctrine conveyed by the Filioque, but gave the advice to omit the expression in the Creed."
That's an excellent tertiary source. Now show us a primary source please as to Pope Leo III's approval and conveyal.