Downing, A. and P. Locke. (1992). A University Course in English Grammar. New York and London: Prentice Hall.
Halliday, M. A. K. (1994). An Introduction to Functional Grammar. 2nd ed. London: Arnold.
Torsello, C. (1984–1992). English in Discourse: A Course for Language Specialists. Vols. 11 & 21. Padua: CLEUP (Cooperativa Libraria Editrice Università di Padova).