1. Atkinson, D., Root studies. Rept. E. Malling Research Sta. 1972, 56?60 (1973).
2. Atkinson, D., The root system of Fortune/M. 9. Rept. E. Malling Research Sta. 1972, 72?78 (1973).
3. Broeshart, H. and Nethsinghe, D. A., Studies on the pattern of root activity of tree crops using isotope techniques. In Isotopes and Radiation in Soil Plant Relationships including Forestry, pp. 453?463. I.A.E.A., Vienna (1972).
4. Brownell, J. R. and L�uchli, A., Measurement of ?-emitters in plant material with Cerenkov radiation: Correction of color-quenching. Intern. J. Applied Radiation Isotopes 20, 797?798 (1969).
5. Dev, G., Bakshi, J. C. and Sharma, P. K., Prelinary studies on grape vine roots for the absorption of phosphorus. In Radiation and Radio-isotopes in Soil Studies and Plant Nutrition, pp. 409?415. Dept. of Atomic Energy, Bombay (1971).