This Bible contradiction is from the Skeptic's Annotated Bible.
Joshua 11:21 View context
And at that time came Joshua, and cut off the Anakims from the mountains, from Hebron, from Debir, from Anab, and from all the mountains of Judah, and from all the mountains of Israel: Joshua destroyed them utterly with their cities.
Joshua 15:13-14 View context
And unto Caleb the son of Jephunneh he gave a part among the children of Judah, according to the commandment of the LORD to Joshua, [even] the city of Arba the father of Anak, which [city is] Hebron.
And Caleb drove thence the three sons of Anak, Sheshai, and Ahiman, and Talmai, the children of Anak.