On 26 February 1814 King William I decreed that the Nederlandsch Israëlitisch Seminarium (NIS) was to be established in Amsterdam to train rabbis, teachers and other officers serving the Jewish community.
Isak Hakker, the son of Nathan, attended the NIS.
In addition, a Jokos file (number 34335) on this family is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.