Garten Jr., C.T., Classen, A.T., Norby, R.J., Brice, D.J., Weltzin, J.F. and Souza, L. 2008. Role of N2-fixation in constructed old-field communities under different regimes of [CO2], temperature, and water availability. Ecosystems 11: 125-137.

Wray, S.M. and Strain, B.R. 1987. Interaction of age and competition under CO2 enrichment. Functional Ecology 1: 145-149.