A. Moghimi and M. Javad Poursharifi, “Solid Phase Extraction of Ultra Trace Amounts of Cobalt and Nickel on Octadecyl Bonded Silica Membrane Disk Modified with N,N?-Bis(3,5-di-tert-butylsalicylidene)- 1,2-diaminoethane and Determination by Inductively C”, ajc, vol. 20, no. 7, pp. 5071–5081, Mar. 2010.