France in the Middle Ages, 987-1460
by
Georges Duby
November 1, 1993, Blackwell Publishing Limited
Papacy and law in the Gregorian revolution
by
Kathleen G. Cushing
1998, Clarendon Press, Oxford University Press
Church, state, and Christian society at the time of the investiture contest
by
Gerd Tellenbach
1991, University of Toronto Press in association with the Medieval Academy of America
Communications and Power in Medieval Europe
by
Karl Leyser
1994
Moyen Age 987-1460
by
Georges Duby
1991
The crisis of church & state, 1050-1300
by
Tierney, Brian.
1964
Before the Gregorian reform
by
Howe, John
2016
The Peace of God
by
Thomas Head
1992