Standard negation is clause-final. Where the main verb takes a complement clause, absolute clause-final position is frequently ambiguous, as illustrated here. Such cases may be disambiguated in one of two ways: First, by the presence of perfective aspect. Because of its unacceptability under negation, its presence signals a failure of negation to scope over the proposition that contains it. Second, right-dislocation of an embedded proposition places it overtly outside the scope of negation.
Source: Kouwenberg 1994: 239
Source: Kouwenberg 2000: 896
Source: Kouwenberg 1994: 88