Pope Pius IV (March 31, 1499 - December 9, 1565), born Giovanni Angelo de Medici, was Pope from 1559 to 1565. He is generally believed to be the first pope to have died leaving "in pectore" cardinals unpublished. Wikipedia
The definitive Wikipedia entry for Pope Pius Pius IV. Wikipedia is the biggest multilingual free-content encyclopedia on the Internet. en.wikipedia.org/wiki/Pope_Pius_IV
