Original sentence: The First Complete Documentation of the Facts behind the Legend, are theorizing that a more plausible timeframe would be 1086-1108, when there were several antipopes, and the reign of the legitimate popes Victor III, Urban II and Paschal II was not always established in Rome, since this city was occupied by Emperor Henry IV, and later sacked by the Normans
Edited sentence: The First Complete Documentation of the Facts behind the Legend, theorize that a more plausible time frame would be 1086-1108, when there were several antipopes, and the reign of the legitimate popes Victor III, Urban II and Paschal II was not always established in Rome, since this city was occupied by Emperor Henry IV, and later sacked by the Normans