Before revision: Senseless but grammatical Chomsky writes in his 1957 book Syntactic Structures: It is fair to assume that neither sentence (1) nor (2) (nor indeed any part of these sentences) has ever occurred in an English discourse.
After revision: Senseless but grammatical Chomsky wrote in his 1957 book Syntactic Structures: It is fair to assume that neither sentence (1) nor (2) (nor indeed any part of these sentences) had ever previously occurred in an English discourse.