Judic Walvis was a daughter of Zacharias Walvis and Fijtje Posener. She married in Amsterdam on 6 February 1918 to Izak van Gelder, son of Salomon van Gelder and Johanna Feitsma.
City Archive of Amsterdam, archive card of Judic Walvis and website www.wiewaswie.nl.
In addition, a Jokos file (number 55602) on this family is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.