Woolbright, S. A., S. P.  Difazio, T.  Yin, G. D.  Martinsen, X.  Zhang, G. J.  Allan, T. G.  Whitham, and P.  Keim. 2008. A dense linkage map of hybrid cottonwood (Populus fremontii x P. angustifolia) contributes to long-term ecological research and comparison mapping in a model forest tree.. Heredity 100:59 - 70.

Fischer, F. G., S. C.  Hart, B. J.  Rehill, R. L.  Lindroth, P.  Keim, and T. Gand Whitham. 2006. Do high-tannin leaves require more roots?. Oecologia 149:668 - 75.