1. GLOBALG.A.P. Integrated Farm Assurance: http://www.globalgap.org/uk_en/what-we-do/
2. European Food Sustainable Consumption and Production (SCP) Round Table www.food-scp.eu/files/Guiding_Principles.pdf
3. On-line mechanical resistance mapping and correlation with soil physical properties for precision agriculture;Sirjacobs;Soil and Tillage Research,2002
4. On-line measurement of some selected soil properties using a VIS-NIR sensor;Mouazen;Soil & tillage research,2007
5. Accuracy issues in electromagnetic induction sensing of soil electrical conductivity for precision agriculture;Sudduth;Comput. Electron. Agric,2001