Rai, H.C., Ashwini Kumar, K.B. Singh, and Raman Kumar. 2012. “Spectrophotometric Determination of Nickel(II) With Phenanthrenequinone Monosemicarbazone”. Asian Journal of Chemistry 16 (1):299-303. https://asianpubs.org/index.php/ajchem/article/view/19625.