Thus suppose that a grammar were to contain the rewriting rules (12) [...] (iii) VP → V⁀NP ('examine Bill'); (iv) VP → V ('leave'); (v) VP → V⁀NP⁀Sentence ('persuade Bill that John left') [...] Main-Verb-of is defined by (iii), (iv) and (v), so that 'examine', 'leave', 'persuade' are the Main-Verbs of the accompanying examples.
- Chomsky (1969), a pag.72

Thus Subject-Verb can be defined as the relation between the Subject-of a Sentence and Main-Verb-of the Predicate-of the Sentence […].
- Chomsky (1969), a pag.73