The 1941 records of the town of Winschoten state that Bertha Geertje Meijer was a daughter of Derkiena Klok from an earlier marriage with Heiman Meijer.
Addition of a visitor of the website.
In addition, a Jokos file (number 54243) on this family is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.