 Calvin also wrote many letters and treatises.Following the "Responsio ad Sadoletum", Calvin wrote an open letter at the request of Bucer to Charles V in 1543, "Supplex exhortatio ad Caesarem", defending the reformed faith.This was followed by an open letter to the pope ("Admonitio paterna Pauli III") in 1544, in which Calvin admonished Paul III for depriving the reformers of any prospect of rapprochement.