Publications
Duffley, Patrick, Sandra Clarke and Walter H. Hirtle. 1981. 'May', 'can' and the expression of permission. The Canadian Journal of Linguistics/La Revue Canadienne de Linguistique 26 (2) : 179–193.
Hoffmann, Ludger. 1979. Permissive. In Velde, Marc Van de and Willy Vandeweghe, eds. Bedeutung, Sprechakte und Texte: Akten des 13. Linguistischen Kolloquiums, Gent 1978, Band 2. M. Niemeyer. pp. 219–228.
Lewis, David K. 1979. A problem about permission. In Saarinen, Esa, Risto Hilpinen, Ilkka Niiniluoto and Merrill Provence Hintikka, eds. Essays in honour of Jaakko Hintikka: On the occasion of his fiftieth birthday on January 12, 1979. Reidel. pp. 163–175.