Barbiers, S., Beukema, F. H., & Wurff, W. v. d. (2002). Modality and its interaction with the verbal system. John Benjamins.

Barbiers, Sjef, F. H. Beukema, and Wim van der Wurff. Modality and Its Interaction with the Verbal System. Amsterdam ; Philadelphia: John Benjamins, 2002.

Barbiers, Sjef, et al. Modality and Its Interaction with the Verbal System. John Benjamins, 2002.