1. Adsett, J.F., Zoerb, G.C., 1991. Automated field monitoring of soil nitrate levels. In Proceedings ASAE symposium on Automated Agriculture for the 21st Century, 16–17 Dec., 1991, Chicago, IL. American Society of Agricultural Engineers, St. Joseph, MI, pp. 326–335.
2. Alihamsyah, T., Humphries, E.G., 1991. On-the-go mechanical impedance measurements. In: Automated Agriculture for the 21st Century, Proceedings of the 1991 Symposium. ASAE, MI, pp. 300–306.
3. Near-infrared analysis as a rapid method to simultaneously evaluate several soil properties;Ben-Dor;Soil Sci. Soc. Am. J.,1995
4. Billings, S., 1994. Airborne radiometrics for the mapping of soils. (Unpublished).
5. Birrell, S.J., Hummel, J.W., 1997. Multi-sensor ISFET system for soil analysis. In: Stafford, J.V. (Ed.), Precision Agriculture '97, Vol. I: Spatial variability in Soil and Crop. Bios Scientific Publishers, UK, pp. 459–468.