1. Alvarez, R., & Grigera, S. (2005). Analysis of soil fertility and management effects on yields of wheat and corn in the rolling Pampa of Argentina. Agronomy and Crop Science, 191, 321–321.
2. Arnall, D. B., & Mullen, R. W. (2011). Review of low and high technology nitrogen management approaches for improved nitrogen use efficiency. In D. E. Clay & J. F. Shanahan (Eds.), GIS applications applications in agriculture. (Vol. 2). CRC Press.
3. Blake, G. R., & Hartge, K. H. (1986). Bulk density. In A. Klute (Ed.), Methods of soil analysis (2nd ed., pp. 363–382). Agronomy Monograph 9, American Society of Agronomy and Soil Science Society of America.
4. Bongiovanni, R., Robledo, C. W., & Lambert, D. M. (2007). Economics of site-specific nitrogen management for protein content in wheat. Computers and Electronics in Agriculture, 58, 13–24.
5. Bremmer, J. M. (1996). Nitrogen total. In D. L. Sparks (Ed.), Methods of soil analysis (5th ed., pp. 1085–1121). Soil Science Society of America.