The Catechism of the Catholic Church reads "often the texts of Sacred Scripture are not quoted literally but merely indicated as a reference ('Cf.') in the footnotes. For a deeper understanding of those passages, the reader should go to the texts themselves. These Biblical references are a working tool for catechesis."
This Companion to the Catechism of the Catholic Church Book of References contains all the passages of Sacred Scripture referred to in the Catechism arranged according to the paragraphs in which the references are made.
But that is only a beginning. The Catechism also refers to conciliar texts, papal documents, writings of the Fathers and of the Saints. There are more than 3,600 of these references extending from the earliest credal formulations of the ancient Church to the documents of Vatican II and beyond to the magisterial teaching of Pope John Paul II. The Book of References includes all the texts referred to arranged, along with the Scripture passages, according to the paragraphs of the Catechism in which they are referred.
This Book of References is a valuable instrument in teaching, understanding, and implementing the Catechism. It is a handy one-volume reference library for use with the Catechism.
"... I ask the Church's pastors and the Christian faithful to receive this Catechism in a spirit of communion and to use it assiduously in fulfilling their mission of proclaiming the faith and calling people to the Gospel life."
— Pope John Paul II