The Origins of the Great Schism: A study in fourteenth century ecclesiastical history, by Walter Ullmann (Hamden, Conn: Archon Books, 1967 (rev. of 1948 original publication)) .
The Origins of the Great Schism: A study in fourteenth century ecclesiastical history, oleh Walter Ullmann (Hamden, Conn: Archon Books, 1967 (revisi dari publikasi orisinalnya pada tahun 1948)).