M. R. Vardast, N. S. A. C. “Optimization of Dispersive Liquid-Liquid Microextraction Followed by Flame Atomic Absorption Determination of Cu (II), Ni (II) and Co (II) Based on the Complexation Reaction With Phenathrene-9, 10-Dine Dioxime (PD)”. Journal of Biomedical and Pharmaceutical Research, Vol. 2, no. 6, Dec. 2013, http://jbpr.in/index.php/jbpr/article/view/342.