Uytven, R. van. “G.S. Gramulla, Handelsbeziehungen Kölner Kaufleute Zwischen 1500 Und 1650”. BMGN - Low Countries Historical Review 89, no. 2 (January 1, 1974): 293–295. Accessed November 24, 2024. https://bmgn-lchr.nl/article/view/URN%3ANBN%3ANL%3AUI%3A10-1-101982.