Machiel Wertheijm and Esther Halverstad married in 1921 in Amsterdam.
Stadsarchief Amsterdam, archiefkaart Esther Halverstad
In addition, Jokos files (numbers 18083, 33882, 61146) on this family or other family members are at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.