Callaway, R.M., DeLucia, E.H., Thomas, E.M. and Schlesinger, W.H.  1994.  Compensatory responses of CO2 exchange and biomass allocation and their effects on the relative growth rate of ponderosa pine in different CO2 and temperature regimes.  Oecologia 98: 159-166.

Constable, J.V.H., Litavk, M.E., Greenberg, J.P. and Monson, R.K.  1999.  Monoterpene emission from coniferous trees in respons to elevated CO2 concentration and climate warming.  Global Change Biology 5: 255-267.

Houpis, J.L.J., Anderson, P.D., Pushnik, J.C. and Anschel, D.J.  1999.  Among-provenance variability of gas exchange and growth in response to long-term elevated CO2 exposure.  Water, Air, and Soil Pollution 116: 403-412.

Olszyk, D.M., Johnson, M.G., Phillips, D.L., Seidler, R.J., Tingey, D.T. and Watrud, L.S.  2001.  Interactive effects of CO2 and O3 on a ponderosa pine plant/litter/soil mesocosm.  Environmental Pollution 115: 447-462.