Sometimes the translator just has to make an interpretive decision. The Greek can mean one thing or something else, and you have to choose. Hebraic (or attributive) genitives often force this type of decision. 2 Corinthians 4:4.

This is a rather technical blog on the nature of Greek appositional constructions. I imagine I lost many of you with that first sentence, but the distinction between the two forms is important exegetically. If you read "x of y," is "y" the same thing as "x" or is "y" explaining something about "x"?