For those asking, it's in section seven, additional clauses: Notwithstanding any other provision of this License, for material you add to a covered work, y

For those asking, it's in section seven, additional clauses: Notwithstanding any other provision of this License, for material you add to a covered work, you may (if authorized by the copyright holders of that material) supplement the terms of this License with terms: [...] c) Prohibiting misrepresentation of the origin of that material, or requiring that modified versions of such material be marked in reasonable ways as different from the original version; or...