Critical study of the Gospels has sought the human Jesus behind the mythic and theological symbols of Christianity. Analysis of material common to Matthew, Mark and Luke and of sayings common to Matthew and Luke (designated 'Q', German Quelle, 'source') has provided an explanation of the sources of the synoptics (Fitzmyer, The Gospel According to Luke (I-IX), pp. 63-106). Mark was the earliest narrative account of Jesus. References to war in Judea (Mark 13:5-8, 14-19) as well as to persecution (8:34-8; 13:9-13) suggested that it was written during Nero's persecution of Christians in Rome or the Jewish revolt in Judea (c. 66-70 CE; see Donahue, 'Windows and Mirrors'). Independently of each other, Matthew and Luke expanded Mark. Their sayings material (Q) came to each evangelist in different forms (cf. Matthew 5:3-10 and Luke 6:20-6; see Betz, The Sermon on the Mount, pp. 22-44,105-10)- Matthew and Luke sometimes substituted the Q version of an episode for Mark's (cf. Mark 1:12-13; Matthew 4:1-11 and Luke 4:1-13). In other cases, oral tradition underlies the agreements of Matthew and Luke against Mark (e.g. Mark 14:65; Matthew 26:68; Luke 22:64).