1. Yu, H., Huang, J., Scott, R., & Loren, B. (2003). Soil fertility changes of cultivated land in eastern China. Resour. Sci., 22(3), 380–388.
2. Wang, J., Zhang, F., Wang, R., Jia, X., & Zhang, C. (2001). Application of integrated fertility index method in evaluating changes in soil fertility. Rural. Eco-Environ, 17(3), 13–16, 20.
3. X. He, (2004) "Comprehensive evaluation and spatial variation of soil fertility in Chengdu plain," Ph.D. dissertation, Dept. College of Environmental Sciences, SAU, Sichuan, China.
4. Yu, H., Huang, J., Scott, R., & Loren, B. (2003). Impact of socio-economic factors on soil fertility over time. Resour. Sci., 25(2), 63–72.
5. Hu, J., Wang, D., Sun, R., Wang, C., & Liu, Q. (2008). Variation of soil fertility of farmlands in typical regions in the lower-reaches of the Yangtze river—A case study of Changshu county. Acta Pedologica Sinica, 45(6), 1087–1094.