Herzog, Günter. “Germany Cologne: ZADIK – Central Archive for German and International Art Market Studies”. State of the Art Archives: International Conference on Archives Documenting Modern and Contemporary Art, edited by ZADIK, basis wien, Institut für moderne Kunst, arthistoricum.net-ART-Books, 2019, pp. 59-74, https://doi.org/10.11588/arthistoricum.426.c6243.