Betje Colthof was a daughter of Izak Colthof and Jenny Hammelburg. She married Louis Verduin on 5 November 1941 in Amsterdam. Stadsarchief Amsterdam, archiefkaart Betje Colthof
In addition, Jokos files (numbers 34237, 34243) on this family or other family members are at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.