Frijhoff, W. 1997. J. Koopmans, Rhetoric - Rhétoriqueurs - Rederijkers. Proceedings of the colloquium, Amsterdam, 10-13 November 1993. BMGN - Low Countries Historical Review. 112, 2 (Jan. 1997), 265–266. DOI:https://doi.org/10.18352/bmgn-lchr.4471.