Human Truth Foundation pages (4):
Who Wrote the Four Gospels of the New Testament? An Introduction to Matthew, Mark, Luke and John., in the following sections:
The Crucifixion in the Bible's Gospels: Differences and Contradictions: 1. Introducing the Gospels
The Gospel According to Saint Mark
The Christian Holy Bible: 2.2. The Four Gospels (Matthew, Mark, Luke and John)