1. Angelo, E., and Potter, G. F., The error of sampling in studying distribution of the root systems of Tung trees by means of the Veihmeyer soil tube. Proc. Amer. Soc. hort. Sci.37, 518–520 (1939).
2. Cahoon, G. A., and Morton, E. S., An apparatus for the quantitative separation of plant roots from soil. Proc. Am. Soc. hort. Sci.78, 593–596 (1961).
3. Hack, H. R. B., An empirical investigation into the distribution of the F-ratio in samples from two non-normal populations. Biometrika45, 260–265 (1958).
4. Hack, H. R. B., Soil moisture tensiometers: some limitations and applications to growth studies. Int. Hort. Congr. 15 Nice1958, 400–417 (1961).
5. Kolesnikov, V. A., Cyclic changes in the roots during the development of top and small fruit plants. Izv. timiryazev. sel'. khoz. Akad.1967 (No. 2), 146–155 (1967).