(Linebarger 1987:338) For example, NPI is grammatical in the next sentence (13), for the reason that negation does not have scope over the because-clause in LF: (11) He didn't budge an inch, because he was just a wooden statue.
(Zwarts 1993;van der Wouden 1997) Zwarts (1993,1998) classifies three types of NPIs which are "weak", "strong", and "superstrong", according to DE-ness, anti-additivity and anti-morphy respectively.