A child of a family among their circle of friends remembers waving goodbye to the Niekerk family when they left to report to the Germans. Isaac came to see his friends in Amsterdam one more time after that, because he had to help to clear the houses of Jews who had been deported. He cried all night long. He was offered a hiding-place, but chose to stay with his family instead. The eldest son, Salomon, was known as Onno.
Addition of a visitor of the website
In addition, a Jokos file (number 55401) on this family is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.The Jokos file reveals that a claim was lodged for compensation for valuables surrendered to the Lippmann-Rosenthal looting bank (L-claim, number 11).