"Episcopal Conferences" in the Catechism of the Catholic Church: Paragraph 887 of the CCC mentions episcopal conferences. From this same page, you can put this paragraph in context by reading the surrounding section of the Catechism.
Apostolos Suos: Apostolic Letter on the Theological and Juridical Nature of Episcopal Conferences, issued motu proprio by John Paul II, 1998.
Episcopal Conferences: Section on bishops' conferences in the 1983 Code of Canon Law.
Episcopal Conferences: Historical, Canonical and Theological Studies: 1989 book, full text online. Scholarly essays by several authors.
On the Authority of Bishops' Conferences: Article by Joseph Komonchak, from the September 12, 1998, issue of America magazine.