How the Church teaches and governs, in the documents the Enciclopedia Cattolica rests on: the letters of the popes, the canons of the councils, the decrees of the Roman congregations, the Code of Canon Law of 1917 and Denzinger's handbook. Each in its own words, and each leading back to the entries that cite it.
The popes
Every pope to Pius XII, each with his article; the encyclicals, bulls, briefs and constitutions by pope and by date.
The councils
The canons of the ecumenical and particular councils, from antiquity to Trent and the Vatican.
The Roman congregations
Decrees and instructions of the Holy Office and the other congregations.
Canon law
The 1917 Code, the law in force when the Encyclopedia was written.
Denzinger
The Enchiridion symbolorum, in the numbering the Encyclopedia used.