1. Ruggie , “Continuity and Transformation in the World Polity,” p. 275
2. Bloch , Feudal Society, p. 410
3. Duby , La société aux XIe et XIIe siècles dans la région mâconnaise, p. 169
4. Watt J. A. , “Spiritual and Temporal Powers,” in Burns , The Cambridge History of Medieval Political Thought, pp. 384–85 and 394