What do I do about my article?

I'm writing an article refuting the claims Dan Brown made in The Da Vinci Code, and I'm stuck with sources. Who do I talk to? What kind of people do I interview? My friend reviewed my work, and he says that I should use sources other than the Bible. I quoted from the Gnostic Gospels, but he said it wouldn't qualify as a source, as I am refuting its claims.