Dawid Borensztajn had a brother with whom he was deported from Westerbork to Theresienstadt. They were subsequently brought to Auschwitz and camp Golleschau. The brother of Dawid Borensztajn survived the war and published his memoirs as 'Togboech'.
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In addition, a Jokos file (number 4891) on this family is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.