When copying data from this family tree, please include a reference to the origin: Gert Jonker, "Family tree Jonker", database, Genealogy Online (https://www.genealogieonline.nl/jonker_stamboom/I25630.php : accessed February 14, 2026), "Willem Kalfsterman".
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Genealogical publications are copyright protected. Although data is often retrieved from public archives, the searching, interpreting, collecting, selecting and sorting of the data results in a unique product. Copyright protected work may not simply be copied or republished.
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.