4711-Haus (in de). cityinfo-koeln.de / Handwerkerzone 32. Retrieved on 2012-08-15.Name and license on the lightbox
Reistips voor na de quarantaine (5): Keulen (in nl). nl.metrotime.be (2020-05-16). Retrieved on 2020-06-06.Name ok, no license, web.archive.org