Following Zvonimir's coronation, the papal legates summoned a church council in Split, which reiterated the ban on the use of Slavic language in liturgy and the condemnation of the Cyrillic alphabet, which the council of 1060 had branded as heresy. The king instituted the Gregorian reform; he also promised the eventual abolition of slavery, but with little success (see Supetar cartulary). He maintained authority over Dalmatia, which could be felt as far as the distant town of Osor on the island of Cres, where he is referenced in a 1082 lauda. He continued the expansive and pro-Roman policies of his predecessor, maintaining a close alliance with the papacy. He made significant donations to the Archbishopric of Split whose head Lawrence had also been his personal advisor.