According to the death records of camp Sachsenhausen Hijman Polak died on 14 January 1945. It is possible this date is different from the official day of death as established after the war by the Department of Justice.
In addition, a Jokos file (number 6887) on this family is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.