When copying data from this family tree, please include a reference to the origin: Kees Helmich, "Family tree Helmich", database, Genealogy Online (https://www.genealogieonline.nl/stamboom-helmich/I2916.php : accessed January 28, 2026), "Cornelis Petrus van der Zwaan (1888-1957)".
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Please stick to the following rules
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.
Do not use this data until you have checked it, preferably at the source (the archives).
State from whom you have copied the data and ideally also his/her original source.