== Eksterne links ==
* [http://www.mapref.org MapRef] {{Webarchive|url=https://web.archive.org/web/20190418082511/http://mapref.org/ |date=18. april 2019 }} - Europäische Referenzsysteme und Kartenprojektionen
* [http://www.gfy.ku.dk/~iag/HB2000/part4/grs80_corr.htm GRS 80 specifikationer] {{Webarchive|url=https://web.archive.org/web/20051225213554/http://www.gfy.ku.dk/~iag/HB2000/part4/grs80_corr.htm |date=25. december 2005 }}
* [https://iag.dgfi.tum.de/fileadmin/handbook/handbook_2016/Handbook_2016.pdf IAG Handbook 2008: ''The Geodesist’s Handbook 2016''] {{Webarchive|url=https://web.archive.org/web/20171222053308/https://iag.dgfi.tum.de/fileadmin/handbook/handbook_2016/Handbook_2016.pdf |date=22. december 2017 }} i ''Journal of Geodesy'', 2016, 90, 10 {{en sprog}}.
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