Christopher Kaczor is a philosophy professor at Loyola Marymount University in Los Angeles and author of The Seven Big Myths About the Catholic Church: Distinguishing Fact From Fiction About Catholicism, in which he discusses the papacy. He can discuss Benedict’s legacy.

Phillip Thompson is executive director of Emory University’s Aquinas Center of Theology. The Aquinas Center is one of four independent Catholic intellectual centers at a non-Catholic U.S. university.

Kenneth Pennington holds the Kelly-Quinn Chair of Ecclesiastical and Legal History at the Catholic University of America and is an expert in church history and canon law. He has written extensively about the papacy.

The Rev. Mark Morozowich is dean of the School of Theology and Religious Studies at The Catholic University of America in Washington, D.C. He can discuss Benedict’s legacy, particularly his contribution to the Eastern churches, and general topics related to the Vatican. Morozowich is an authority on early Christian liturgy and eastern Churches (Orthodox and Catholic).

Monsignor Kevin Irwin is professor of liturgical studies at the Catholic University of America. He can discuss the progression of Benedict’s views on human stewardship of natural resources in his major discourses of moral teaching.

The Rev. Matthew Fox is a former Dominican priest who was silenced by the Vatican in 1988 for his theological writings. Fox is now an Episcopal priest. He is the author of a 2011 book, The Pope’s War: Why Ratzinger’s Secret Crusade Has Imperiled the Church and How It Can Be Saved.

Image Books, a division of Random House, has published many of Pope Benedict XVI’s English-language books, including his most recent. In addition, Image published the Spanish-language edition of The Infancy Narratives in the United States in February 2013.

Read the text of Pope Benedict XVI’s resignation announcement.

NBC News posted a timeline of the pope’s life on Feb. 11, 2013.