Butts, C.L., J.W. Mishoe and K.V. Chau. 1990. Measuring Thermal Diffusivity of Soil. Transactions of ASAE 33(1):179-184.

Cairo, G., D.L. Larson, and D.C. Slack. 1992. Electro-osmotic removal of Nitrates from Soils. Paper 92-3531. St. Joseph, Michigan: American Society of Agricultural Engineers.

Cullum, R.F. 1993. Soil Water Content Evaluation of Tillage Practices from an Automated Multiplexed System for Measuring Dielectric Constant. Paper 93-3087. St. Joseph, Michigan: American Society of Agricultural Engineers.

Freeland, R.S. 1989. Review of Soil Moisture Sensing Using Soil Electrical Conductivity. Transactions of ASAE 32(6):2190-2194.

Freeland, R.S., L.M. Callahan and R.D. von Bermuth. 1990. Instrumentation for Sensing Rhizosphere Temperature and Moisture Levels. Applied Engineering in Agriculture 6(2):219-223.

Graf, G.L. and J.R. Cooke. 1980. Soil Stresses around a Growing Root Tip. Paper 80-1024, American Society of Agricultural Engineers, St. Joseph, Michigan.

Han, Y.J. and V.L. Quisenberry. 1991. Image Analysis Procedure to Quantify Soil Macropore Structure. Applied Engineering in Agriculture 7(5):636-642.

Heathman, G.C. 1993. Soil Moisture Determination using a Resonant Frequency Capacitance Probe. Paper No. 93-1053. St. Joseph, Michigan: American Society of Agricultural Engineers.

Huang, C. and J.M. Bradford. 1990. Portable Laser Scanner for Measuring Soil Surface Roughness. Soil Science Society of American Journal 54(5):1402-1406.

Luo, X. and L.G. Wells. 1992. Evaluation of Gamma Ray Attenuation for Measuring Soil Bulk Density Part I. Laboratory Investigation. Transactions of ASAE 35(1):17-26/

Morgan, M.T., R.K. Wood, and R.G. Holmes. 1993. Dielectric Moisture Measurement of Soil Cores. Transactions of ASAE 36(1):17-22.

McMurtrey, J.E., III, E.W. Chappelle, C.S.T. Daughtry, and M.S. Kim. 1993. Flourescence and Reflectance of Crop Residue and Soil. Journal of Soil and Water Conservation 48(3):207-213.

Shonk, J.L., L.D. Gaultney, D.G. Schulze, and G.E. Van Scoyoc. 1991.Spectroscopic Sensing of Soil Organic Matter Content. Transactions of ASAE 34(5):1978-1984.

Sudduth, K.A. and J.W. Hummel. 1991. Evaluation of Reflectance Methods for Soil Organic Matter Sensing. Transactions of ASAE 34(4):1900-1909.

Sudduth, K.A. and J.W. Hummel. 1993. Portable Near-Infrared Spectophotometer for Rapid Soil Analysis. Transactions of ASAE 36(1):185-193.

Tollner, E.W. and C. Murphy. 1991. Factors Affecting Soil X-Ray Absorption Coefficients with Computer Tomography. Transactions of ASAE 34(3):1047-1053.

Welles, J.M. and J.M. Norman. 1991. Instrument for Indirect Measurement of Canopy Archtecture. Agronomy Journal 83:818-825

Wells, L.G. and X. Luo. 1992. Evaluation of Gamma Ray Attenuation for Measuring Soil Bulk Density Part II. Field Investigation. Transactions of ASAE 35(1):27-32.