S. Thatipally, P. V.R. Acharyulu, and P. K. Dubey, “Pyridinium p-Toluenesulfonate: A Mild and Efficient Catalyst for The Regioselective Tetrahydropyranylation of Indazole Derivatives Under Solvent-Free Conditions”, ajc, vol. 23, no. 1, pp. 451–454, Sep. 2010.