Hussein, H.F., Saber, M.S.M., Radwan, S.M.A. and Abu- Seda, M. (2004) Use of treated domestic sewage effluent for growing summer oil crops in arid lands. International Conference on Water Resources & Arid Environment, King Saud University, Riyadh, 5-8 December,1-16.
 O’Riordan, E.G., Dodd, V.A., Fleming, G.A. and Tunney, H. (1987) The fertilizer nutrient value of an aerobically degested sewage sludges under grassland field conditions. Irish Journal of Agricultural and Food Research, 26, 199-211.
 Fatoki, O.S. (2000) Trace zinc and copper concentration in road side vegetation and surface soils: A measurement of local atmospheric pollution in Alice, South Africa. International Journal of Environmental Studies, 57, 501513.
 Tokalioglu, S., Kartal, S. and Gunis, A.A. (2000) Determination of heavy metals in soil extracts and plant tissues at around of zinc smelter. International Journal of Environmental Analytical Chemistry, 80, 210-217.
 Eick, M.J., Peak, J.D., Brady, P.V. and Pesek, J.D. (1999) Kinetics of lead adsorption and desorption on goethite: Residence time effect. Soil Science, 164, 28-39. doi:10.1097/00010694-199901000-00005
 Kumar, N.P.B.A., Dushenkov, V., Motto, H. and Raskin, I. (1995) Phytoextraction: The use of plants to remove heavy metals from soils. Environmental Science and Technology, 29, 1232-1238. doi:10.1021/es00005a014
 Arizmendi-Maldonado, D., McDowell, L.R., Sinclair, T. R., Mislevy, P., Martin, F.G. and Wilkinson, N.S. (2001) Mineral concentrations in four tropical forages as affected by increasing daylength. II. Microminerals. Communications in Soil Science and Plant Analysis, 33, 2001-2009. doi:10.1081/CSS-120004838
 Fick, K.R., McDowell, L.R., Miles, P.H., Wilkinson, N. S., Funk, J.D. and Conrad, J.H. (1979) Methods of mineral analysis for plant and animal tissues. 2nd Edition, Department of Animal Science, University of Florida, Gainesville.
 Ahmad, K., Khan, Z.I., Ashraf, M., Valeem, E.E., Shah, Z. A. and McDowell, L.R. (2009) Determination of forage concentration of lead, nickel and chromium in relation to the requirements of grazing ruminants in the salt range. Pakistan Journal of Botany, 41, 61-65.
 Tokalioglu, S. and Kartal, S. (2005) Determination of Cu, Pb, Cd, Ni, Cr, Co, Mn, Fe and Zn in algae and vegetable samples using wet and dry ashing procedure. Trace Element & Electrocytes, 22, 169-173.
 Ahmad, K., Khan, Z.I., Ashraf, M.Y., Ashraf, M. and Valeem, E.E. (2008) Forage evaluation for some trace elements: A case study in the soone valley, Pakistan. Pakistan Journal of Botany, 40, 999-1004.
 Hue, N.V., Silva, J.A. and Arifin, R. (1988) Sewage sludge-soil interactions measured by plant and soil chemical composition. Journal of Environmental Quality, 17, 384- 390. doi:10.2134/jeq1988.00472425001700030007x