This April 24, 2005 file photo shows Pope Benedict XVI,center, holding a cross as he celebrates his installment Mass in St. Peter's Square, at the Vatican, Sunday, April 24, 2005. Benedict XVI announced Monday, Feb. 11, 2013, that he would resign on Feb. 28 because he was simply too infirm to carry on - the first pontiff to do so in nearly 600 years. The decision sets the stage for a conclave to elect a new pope before the end of March. (AP Photo/Andrew Medichini, files)