Cheng, X., Luo, Y., Su, B., Verburg, P.S.J., Obrist, D., Arnone, J.A. III, Johnson, D. W., Evans, R. D. (2009). Responses of Net Ecosystem CO2 Exchange to Nitrogen Fertilization in Experimentally Manipulated Grassland Ecosystems, Agricultural and Forest Meteorology, 149, 1956-1963