Il nipotismo di Roma, or, The History of the Popes Nephews from the time of Sixtus IV. to the death of the last Pope, Alexander VII

The History of the Popes: From the Foundation of the See of Rome, to the Present Time, 3rd Ed. Vol. 1

Archibald Bower

Peter's Rock in Mohammed's Flood, from St. Gregory the Great to St. Leo III

T. W. Allies

Crises in the History of the Papacy A study of twenty famous popes whose careers and whose influence were important in the development of the church and in the history of the world

Joseph McCabe

Pius IX. And His Time

Æneas MacDonell Dawson

The Power of the Popes An Historical Essay on Their Temporal Dominion, and the Abuse of Their Spiritual Authority

P. C. F. Daunou

The Prince

Niccolò Machiavelli