Gerritje Heijkoop in entry for Johannes Gerardus Zoetmulder and Dirkje Hartman, "Netherlands, Archival Indexes, Miscellaneous Records"
"Nederland, Indexen van de Archieven, Primaire Archiefstukken (BS en DTB), 1600-2000," database,
FamilySearch (
https://familysearch.org/ark:/61903/1:1:Q2X3-TRFJ : 22 August 2017), Gerritje Heijkoop in entry for Johannes Gerardus Zoetmulder and Dirkje Hartman, Marriage 31 Jul 1901, Rotterdam, South Holland, Netherlands; from database,
openarchives (https://www.openarch.nl : 2016); citing ; Burgerlijke Stand Rotterdam, huwelijksakten; Stadsarchief Rotterdam.