Many scholars believe Matthew and Luke drew on two main sources in writing their gospels: Mark’s gospel and Q (from Quelle, German for “source”), a hypothetical “fifth gospel” containing sayings of Jesus. See the following articles in Bible Review: Stephen J. Patterson, “Q—The Lost Gospel,” BR 09:05; Eta Linnemann, “Is There a Gospel of Q?” BR 11:04; and Patterson’s response to Linnemann, “Yes, Virginia, There Is a Q,” BR 11:05.