D. M.  Pore, Soudagar, M. S., Desai, U. V., Thopate, T. S., and Wadagaonkar, P. P., ?Potassium phosphate or silica sulfuric acid catalyzed conjugate addition of thiols to alpha,beta-unsaturated ketones at room temperature under solvent-free conditions?, Tetrahedron Letters, vol. 47, no. 52, pp. 9325-9328, 2006.