Gratian and the Decretum Gratiani / Peter Landau. . In: Thehistory of medieval canon law in the classical period, 1140 - 1234 : from Gratian to the Decretals of Pope Gregory IX / ed. by Wilfried Hartmann .... Washington, DC : Catholic Univ. of America Press, 2008, S.2254
 

Gratian and the Decretum Gratiani