Check the information Open Archives has about De Groot.
Check the Wie (onder)zoekt wie? register to see who is (re)searching De Groot.
The Spier wereldwijd onderzoek publication was prepared by Jan Nienhuis (contact is not possible).
When copying data from this family tree, please include a reference to the origin: Jan Nienhuis, "Spier wereldwijd onderzoek", database, Genealogy Online (https://www.genealogieonline.nl/stamboom-spier/I2448.php : accessed February 16, 2026), "Kalmon de Groot".
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Request permission to copy data or at least inform the author, chances are that the author gives permission, often the contact also leads to more exchange of data.
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