[…] the symbols representing lexical categories (N, V, etc.) will be analyzed by the rules into 'complex symbols', each complex symbol being a set of specified syntactic features […].
- Chomsky (1969), Pag. 82

The lexicon was described [...] simply as a set of lexical entries, each consisting of a distinctive feature matrix 'D' and a complex symbol 'C', the latter being a set of features of various sorts (syntactic and semantic features, features that specify which morphological or transformational processes apply to strings containing the items in question, features that exempt items from certain phonological rules, and so on).
- Chomsky (1969), Pag. 164