his mother https://www.joodsmonument.nl/nl/page/689920/sara-de-hartog-leemans
https://archief.amsterdam/indexen/deeds/985333f7-8278-56a3-e053-b784100ade19?person=985333f7-8279-56a3-e053-b784100ade19
https://www.maxvandam.info/humo-gen/family/1/F23634?main_person=I63738
He died in 1972: https://www.online-begraafplaatsen.nl/graf/1992789/3187171/Frederik-de-Hartog-1892-1972