D. Zhumadullaev, N. Kornauhova, N. Zakarina, and A. Niyazbaeva, “Effect of PW12–GPK on the acid characteristics of Ni-, Pd- and Pt- catalysts deposited onto pillared Al montmorillonite”, Chemical Bulletin of Kazakh National University, vol. 65, no. 1, pp. 253-256, Mar. 2012.