Martin van Rooyen was a prominent member of the 'Nederlandse Jeugdbond voor Natuurstudie (NJN)', together with his good friend 518120.
G. Harmsen, Herfsttijloos (Colchicum autumnale) : een levensverhaal (Nijmegen 1993), 125-125, 160, 629
In addition, a Jokos file (number 17826) 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 …