Pope Silvester III. When Boniface IX was driven from Rome early in January 1044, John, bishop of Sabina, was elected in his stead and took the title of Silvster III. Within three months Boniface returned and expelled his rival. Nearly three years later (December 1046) the council of Sutri deprived him of his bishoprics and priesthood. He was then sent to a a monastery, where he seems to have died.
from the 9th edition (1887) of an unnamed encyclopedia.