"Netherlands, Noord-Holland, Civil Registration, 1811-1950," database with images, FamilySearch (
https://www.familysearch.org/ark:/61903/1:1:Q2H6-K73G : 18 May 2020), Johannes Coerdes in entry for Ferdinand Coerdes, 22 Jul 1834; citing Birth Registration, Amsterdam, Noord-Holland, Nederland, Noord-Hollands Archief (Noord-Hollands Archives), Haarlem; FHL microfilm 113,580.