Guo, Z., K. Hua, J. Wang, X. Guo, C. He, and D. Wang. “Effects of Different Regimes of Fertilization on Soil Organic Matter under Conventional Tillage”. Spanish Journal of Agricultural Research, Vol. 12, no. 3, July 2014, pp. 801-8, doi:10.5424/sjar/2014123-4859.