1. Afridi, M.M.R.K., Samiullah, and Ahmad, A., in: Recent Researches in Plant Sciences, p. 381. Ed. S.S. Bir. Kalyani Publishers, New Delhi 1979.
2. Ahmad, A., Afridi, M.M.R.K., Samiullah, and Inam, A., Comp. Physiol. Ecol.7 (1982) 170.
3. Bonner, J., and Bonner, H., Vitam. Horm.6 (1948) 225.
4. Almestrand, A., Physiologia Pl.3 (1950) 293.
5. Fries, N., Experientia11 (1955) 232.