1. Davenport, H. (1899). Experimental Morphology. Pt. 2. London.
2. Farmer, J. B. (1919). On the quantitative differences in the water conductivity in trees and shrubs. Proc. Roy. Soc. B.90, 218.
3. Fisher, R. A. (1936). Statistical Methods for Research Workers. 6th. edn. London.
4. Flügge, C. (1896). Mikroorganismen. 3. Aufl.,1, 135. Leipzig.
5. Freundlich, H. (1935). Thixotropy. Actualités scientifiques et industrielles. Paris.