S, C. J., and P. A. V. “SYNTHESIS, CHARACTERIZATION AND SPECTROPHOTOMETRIC DETERMINATION OF NI (II) ION BY PYRIDINE 2, 3 DICARBOXYLIC ACID ”. International Research Journal of Pharmaceutical and Applied Sciences, Vol. 3, no. 5, Oct. 2013, pp. 31-36, https://scienztech.org/index.php/irjpas/article/view/486.