Sources:
- All Frisian people: https://allefriezen.nl
- Open Archives: https://www.openarch.nl
- Whowaswho: https://www.wiewaswie.nl
- CBG: https://www.cbg.nl
- Genealogy Online: https://www.genealogieonline.nl
- Family Search: https://www.familysearch.org
- Family members who gave information about their family
Links:
- Family tree of a linked family Hofer: https://www.hofer.nl
- Aldfaer software: http://www.aldfaer.net