When copying data from this family tree, please include a reference to the origin: Knaap, van der Adri (Aad), "Genealogie: van der Knaap - Rotterdam ", database, Genealogy Online (https://www.genealogieonline.nl/genealogie-van-der-knaap/I444.php : accessed May 9, 2024), "Willem van Leeuwen".
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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).
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