https://www.familysearch.org/tree/person/sources/K2KH-TH9
"Nederland, Indexen van de Archieven, Primaire Archiefstukken (BS en DTB), 1600-2000," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:QLMN-FJ36 : 22 August 2017), Christian Pröpper and Grietje Koenen, Marriage 30 Apr 1834, Amsterdam, Noord-Holland, Netherlands; from database, openarchives (https://www.openarch.nl : 2016); citing Haarlem, inventory number , record number Reg.1 fol. 126; ; Noord-Hollands Archief.