== Eksterne links ==
* [http://www.dnagardens.com/what_is_soil_fertility.htm Hvad er jordens frugtbarhed?] {{Webarchive|url=https://web.archive.org/web/20061205043358/http://dnagardens.com/what_is_soil_fertility.htm |date= 5. december 2006 }} (engelsk).
* [http://anrcatalog.ucdavis.edu/pdf/7249.pdf University of California: ”Soil Fertility Management for Organic Crops”] {{Webarchive|url=https://web.archive.org/web/20070113005352/http://anrcatalog.ucdavis.edu/pdf/7249.pdf |date=13. januar 2007 }} (engelsk PDF)
* [http://web.aces.uiuc.edu/faq/faq.pdl?project_id=16 University of Illinois: ”Soil Fertility Management”] {{Webarchive|url=https://web.archive.org/web/20070202173300/http://web.aces.uiuc.edu/faq/faq.pdl?project_id=16 |date= 2. februar 2007 }} (engelsk)
* [http://sungaya.de/schwarz/allmende/goetter/muttergott.htm Frugtbarhed og modergudinden] {{Webarchive|url=https://web.archive.org/web/20070206120215/http://www.sungaya.de/schwarz/allmende/goetter/muttergott.htm |date= 6. februar 2007 }} (tysk)
* [http://www.uni-koeln.de/pi/i/2000.069.htm Köln Universitäts presseinformation om Demeterkulten på Sicilien] {{Webarchive|url=https://web.archive.org/web/20070503080936/http://www.uni-koeln.de/pi/i/2000.069.htm |date= 3. maj 2007 }} (tysk)
* [http://www.gov.mb.ca/agriculture/soilwater/soilfert/fbd01s05.fr.html Canadas landbrugsministerium om jordens frugtbarhed] {{Webarchive|url=https://web.archive.org/web/20070930182943/http://www.gov.mb.ca/agriculture/soilwater/soilfert/fbd01s05.fr.html |date=30. september 2007 }} (fransk)
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Erhvervsliv Teknologi Jordbrug