Cognomen Koolstra (Koolstra 
) , worldwide, is a rare surname. The last name Koolstra is characteristic of Netherlands, where it is quite a rare surname, Australia, where it is a very rare surname, and Canada. Measured by absolute frequency, the name is most common in Netherlands, the United States, and Indonesia.
| VARIANT | COUNTRY |
|---|---|
| Koolstra | Indonesia, Australia, United States, Canada, Netherlands |
| w. koolstra Dutch photographer, NL (b. 1862) |
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| albertus koolstra (b. 1865) |
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| meindert koolstra NL (b. 1917) |
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| kirsten koolstra researcher (ORCID 0000-0002-7873-1511) |
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| g. koolstra researcher ORCID ID = 0000-0002-6574-5789, US |
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| jan harm koolstra researcher |
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