Older volumes which might be worth looking at include, if you have not already used them, Walter Ullmann, The growth of Papal Government in the Middle Ages, esp. chapters III through V, and the works of Ernst Kantorowicz, both The King's Two Bodies and Laudes regiae. There is a brief passage in Marc Bloch, The royal Touch, pp. 264-65. There is some discussion of Charlemagne, but not specific mention of Leo, in Colette Beaune, The Birth of an Ideology. tmi %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%