1. Kinzel, W. Frost und Licht als beeinflussende Krafte der Samenkeimung (Ulmer, Stuttgart, (1920).
2. Toole, V. K. Seed Sci. Technol. 1, 339–396 (1973).
3. Grime, J. P. & Jarvis, B. C. in Light as an Ecological Factor II (eds Bainbridge, R., Evans, G. C. &Rackham, O.) 525–532 (Blackwell, Oxford, (1975).
4. Grime, J. P. et al. J. Ecol. 69 (in the press).
5. McCullough, J. M. & Shropshire, W. Pl. Cell Physiol. 11, 139–148 (1970).