Salehin, S., Aburizaiza, A. S., Barakat, M. A. (2015). 'Recycling of Residual Oil Fly Ash: Synthesis and Characterization of Activated Carbon by Physical Activation Methods for Heavy Metals Adsorption', International Journal of Environmental Research, 9(4), pp. 1201-1210. doi: 10.22059/ijer.2015.1010