I guess by "credit" I meant a phone call or message saying "your Trek novels were an immense help in influencing how we might want to portray the character in our upcoming film. Thanks, Mr. Cox, for helping educate us a little bit." That kind of thing.
There was obviously nothing on screen that could be credited to your books, though it would have been cool had Khan himself mentioned he'd been the product of a classified genetic engineering project called Chrysalis that was carried out on the Indian subcontinent. 

