The origins of the great schism:
Ullmann, Walter
The origins of the great schism: a study in 14th century ecclesiastical history by Walter Ullmann - New York Archon Books 1972
020801277X
Schism, The Great Western
The origins of the great schism: a study in 14th century ecclesiastical history by Walter Ullmann - New York Archon Books 1972
020801277X
Schism, The Great Western