Dutton, Paul Edward (1990): «Beyond the Topos of Senescense: The Political Problems of Aged Carolingian Rulers» i: Sheehan, Michael M.: . Pontifical Institute of Medieval Studies. Geary, Patrick J. (2006): . Princeton University Press. Goldberg, Eric Joseph (2006): . Cornell University Press. Gwatkin, Henry Melvill et al, red. (1957): , , Macmillan. McKitterick, Rosamond (1999): . Longman. Reuter, Timothy (2013): . Routledge. Riche, Pierre (1993): , University of Pennsylvania Press. Walsh, Michael J. (2007): . Liturgical Press.