1. Daniels, F.: Direct Use of the Sun's Energy (8. Ed.), New Haven, Yale University Press 1975
2. Meinel, A. B., Meinel, M. P.: Applied Solar Energy. Reading/Mass., Addison-Wesley 1976
3. Moesta, H.: Naturwissenschaften 63, 491 (1976)
4. Reisfeld, R.: Naturwissenschaften 66, 1 (1979)
5. Sørensen, B.: Renewable Energy. London, Academic Press 1979