from the fourth through twelfth centuries, reserved to the bishop of Rome from the twelfth through early twentieth centuries, and restored to all bishops at the Second Vatican Council. The pope resides in Vatican City, an independent state within the city of Rome, set up by the 1929 Lateran Pacts between the Holy See and Italy. As popes were sovereigns of the papal states (754–1870), so do they exercise absolute civil authority in the microstate of Vatican City since 1929. Ambassadors are accredited not to the Vatican City State but to the Holy See, which was subject to international law even before the state was instituted. The body of officials that assist the Pope in governance of the Church as a whole is known as the Roman curia. The term "Holy See" (i.e. of Rome) is generally used only of the Pope and the curia, because the Code of Canon Law, which concerns governance of the Latin Church as a whole and not internal affairs of the see (diocese) of Rome itself, necessarily uses the term in this technical sense. Finally, the title "Servant of the servants of God" was an addition of Pope Gregory the Great, a reminder that in Christianity, leadership is always about service/ministry (diakonia). The style of address for the bishop of Rome is "His Holiness". Election The present rules governing the election of a pope are found in the apostolic constitution Universi Dominici Gregis. This deals with the powers, from the death of a pope to the announcement of his successor's election, of the cardinals and the departments of the Roman curia; with the funeral arrangements for the dead pope; and with the place, time and manner of voting of the meeting of the cardinal electors, a meeting known as a conclave. This word is derived from Latin com- (together) and clavis (key) and refers to the locking away of the participants from outside influences, a measure that was introduced first as a means instead of forcing them to reach a decision. Like all bishops, the pope has the option of resigning, though unlike other bishops, it is not required. The best known cases are those of Pope Celestine V in 1294, Pope Gregory XII in 1415 and Pope Benedict XVI in 2013. Approximately 10% of all popes left or were removed from office before death. Eastern Patriarchs The heads of some autonomous (in Latin,