Stuart's "Royalty For Commoners (265:41). Maurice Chaume, in Table 4 of v.4 of "Les origines du duche de Bourgogne" (Dijon, 1925-31). Guido was marquis of Spoleto from 842 to 858. There was civil war in the neighboring duchy of Benevento from 839 to 849. Chris Wickham, in
"Early Medieval Italy" makes passing mention that KING LOUIS II OF ITALY and Guy I of Spoleto ended that civil war by dividing Benevento between them. The rulers of Spoleto and Benevento, though technically subservient to the king of Italy were, in actual fact, sovereign princes.