In addition, a Jokos file (number 10775) on this family is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.
GenLias has the marriage record for Philip Nathan and Judic Witteboon. It also notes that Philip Cohen is known as Philip Nathan:
Huw 13-06-1912 Amsterdam #reg.6D;fol.22: Philip Nathan 21 jaar g. Amsterdam, beroep Diamantslijper (Joseph Nathan, beroep Diamantslijper en Anna van Gelder) en Judic Wit…