T. de A. D. dos Santos, D. O. da Costa, S. S. da R. Pita, and F. S. Semaan, “Potentiometric and conductimetric studies of chemical equilibria for pyridoxine hydrochloride in aqueous solutions: simple experimental determination of pKa values and analytical applications to pharmaceutical analysis”, Eclet. Quim., vol. 35, no. 4, pp. 81–86, Dec. 2010.