Pope John X
The "Historia Salonitana", whose composition may have begun in the late 13th century, cites a letter of Pope John X to Tomislav, "king ("rex") of the Croats", in which he refers to the first council in some detail. If the letter is authentic, it shows that the council was attended not only by the bishops of Croatian and Byzantine Dalmatia, but also by Tomislav, whose territory also included the Byzantine cities of Dalmatia, and by a number of Michael's representatives. In this letter, John describes Michael as "the most excellent leader of the Zachlumi" ("excellentissimus dux Chulmorum").