Prohibitives and imperatives, modality, negation, Jespersen's cycle, semantic maps, grammaticalization, areal typology, the dialect syntax of Dutch, scalar particles, indefiniteness, impersonal constructions, and raising.
Editing The Handbook or Mood and Modality (Oxford: Oxford University Press), together with Jan Nuyts
Strongly involved in the editing of Linguistics (Berlin & New York: Mouton de Gruyter) and Langages (Paris: Arman Collin)
Editing a journal theme issue on the diachrony of modal verbs in World Englishes, together with Dirk Noël and Bertus Van Rooy
Editing a book on modality in English, together with Juana I. Marín-Arrese, Marta Carretero Lapeyre and Jorge Arús Hita