Ayad, Magda Mohamed, et al. “Conductometric Titration Method for Determination of Naftidrofuryl Oxalate, Propafenone HCl and Sotalol HCl Using Silver Nitrate”. European Journal of Chemistry, vol. 3, no. 3, Sept. 2012, pp. 332-6, doi:10.5155/eurjchem.3.3.332-336.637.