N. Montazeri, K. Pourshamsian, R. Kalantarian, and M. Mehdi Kia, “Silica Gel-Supported Poly Phosphoric Acid Catalyzed One-Pot Multi-Componen Synthesis of 2,4,6-Triarylpyridines under Solvent-Free and Microwave Irradiation Conditions”, ajc, vol. 24, no. 8, pp. 3751–3753, Apr. 2012.