Sara Boeken was a daughter of Isaäc Boeken (1865-1940) and Mietje Brander (1863-1899). Neeltje Koster was her stepmother. Stadsarchief Amsterdam, archiefkaart Isaäc Boeken
In addition, Jokos files (numbers 31406, 9175) on this family or other family members are at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.