Wright, J. W., Amiel, R. J., Cech, F. C., Kriebel, H. B., Jokela, J. J., Lemmien, W. A., Matheson, A. C., Merritt, C., Read, R. A., Roth, P., Thor, E., Thulin, I. J., (1979). Proceedings of the 26th Northeastern Forest Tree Improvement Conference, July 25-26, 1978. Contributed papers., 203-217. Northeastern Forest Experiment Station., Durham, USA. English language