1. Ahmad, G. C., 1941. Effect of light intensity and temperature on the growth of Azolla filiculoides. J. indian hot. Soc. 20: 213–226.
2. Apaon, A. L., 1939. A study of the growth of rice plants, 2. Effect of shading on can grown plants. Philippine Agric. 27: 818–843.
3. Ashby, E., 1929. The interaction of factors on the growth of Lemna, 3. The interaction of duration and intensity of light. Ann. Bot. 43: 333–354.
4. Ashton, P. J., 1974. The effect of some environmental factors on the growth of Azolla filiculoides Lam. In E. M. v. Zinderen Bakker Sr. (ed.), The Orange River Progress Report. Inst. envir. Sci., Univ. O.F.S. Bloemfontein, S. Africa: 123–138.
5. Ashton, P. J., 1977. Factors affecting the growth and development of Azolla filiculoides Lam. In A. A. Balkema (ed.), Proc. 2nd Nat. Weeds Confrn. S. Africa. Stellenbosch Univ., S. Africa: 249–268.