W. Frijhoff, “J. Koopmans, Rhetoric - Rhétoriqueurs - Rederijkers. Proceedings of the colloquium, Amsterdam, 10-13 November 1993”, BMGN-LCHR, vol. 112, no. 2, pp. 265–266, Jan. 1997, doi: 10.18352/bmgn-lchr.4471.