1. McCree, K. J., in Productivity of Photosynthetic Systems; Models and Methods, Trebon, Czechoslovakia, 1969, Proceedings of the IBP/PP technical meeting (in the press).
2. Pirt, S. J., Proc. Roy. Soc., B, 163, 224 (1965).
3. Warren Wilson, J., in The Collection and Processing of Field Data (edit. by Bradley, E. F., and Denmead, O. T.), 96 (Interscience, New York, 1967).