Heny, Frank and
Richard, Barry, eds. 1983a.
Linguistic Categories: Auxiliaries and Related Puzzles. Volume I: Categories.
Synthese Language Library n. 19. Dordrecht: D. Reidel Publishing Co.
Heny, Frank and
Richard, Barry, eds. 1983b.
Linguistic Categories: Auxiliaries and Related Puzzles. Volume II: The Scope, Order, and Distribution of English Auxiliary Verbs.
Synthese Language Library n. 20. Dordrecht: D. Reidel Publishing Co.