Catholic Encyclopedia: Bulla Aurea (Golden Bull) - Law issued by Charles IV in 1356 that transformed the empire from a monarchy into an aristocratic federation in which seven Electors voted on new emperors.
Holy Roman Empire, The - Originated with the coronation of Otto I in 962 and endured until Francis II renounced his imperial title in 1806. Features the role of the emperor and Reichstag, structure of the empire, and more.
Medieval Sourcebook: Empire and Papacy - Documents related to the Investiture Controversy, Emperor Frederick I Barbarossa, Pope Innocent III, Frederick II, and the medieval Papacy.