Pervin, S., M. S. Hoqlle, M. Iahiruddin, and M. H. Mian. “?EFFECTS OF UREA, AZOLLA AND SESBANIA INCORPORATION ON THE CONCENTRA- TION AND UPTAKE OF N, P, K AND S IN RICE (ORYZA SATIVA)”. Biological Sciences - PJSIR, vol. 42, no. 3, June 1999, pp. 145-9, http://v2.pjsir.org/index.php/biological-sciences/article/view/2137.