1. Billings, W.D., Morris, R.J.: Reflection of visible and infrared radiation from leaves of different ecological groups. Am. J. Bot. 38, 327?331 (1951)
2. Björkman, O.: Comparative studies on photosynthesis in higher plants. In: Photophysiology, Vol. 8, pp. 1?63. New York: Academic Press 1973
3. Björkman, O., Holmgren, P.: Adaptability of the photosynthetic apparatus to light intensity in ecotypes from exposed and shaded habitats. Physiol. Plant. 16, 889?914 (1963)
4. Björkman, O., Nobs, M., Berry, J., Mooney, H.A., Nicholson, F., Catanzaro, B.: Physiological adaptation to diverse environments: approaches and facilities to study plant responses to contrasting thermal and water regimes. Carnegie Inst. Wash. Yb. 72, 393?403 (1973)
5. Clausen, J.D., Keck, D., Hiesey, W.M.: Experimental studies on the nature of species. I. The effect of varied environments of western North American plants. Carnegie Inst. Washington Publ. 520 (1940)