S.  Selvakumar, Chidambaram, M., and Singh, A. P., ?Benzylsulfonic acid functionalized mesoporous Zr-TMS catalysts: an efficient and recyclable catalyst for the preparation of coumarin derivatives by pechmann condensation reaction?, Catalysis Communications, vol. 8, no. 5, pp. 777-783, 2007.

S.  Selvakumar and Singh, A. P., ?Benzoylation of anisole over silicotungstic acid modified mesoporous alumina?, Catalysis Letters, vol. 128, no. 3-4, pp. 363-372, 2009.