The electronic version of the celebrated Registres et lettres des Papes du XIIIe siècle (32 vols.; Rome, 1883- ) and the Registres et lettres des Papes du XIV e siècle (48 vols.; Rome, 1899- ). Furthermore, it contains unpublished material (litterae communes of Gregory XI from 1371 to 1375 and the registers of petitions of Urbain V)--this part of the database represents more than 62,000 documents.
Ut per litteras apostolicas provides striking information on the most varied aspects of medieval society: church institutions, the clergy, the papal states, politics, the legal system, taxation, government and finance, secular society, the religious life, intellectual and artistic life, the economy, wars, law and order, the environment and natural disasters, and daily life. More than 220,000 documents providing insights into the most varied aspects of medieval society.