Kumar Singh, Narendra, et al. “Enhancement of Anticancer Activity of N(4)1-(2-Pyridyl)piperazinyl 5-Nitroisatin Thiosemicarbazone on Chelation With Copper(II)”. Asian Journal of Chemistry, vol. 33, no. 3, Feb. 2021, pp. 557-64, doi:10.14233/ajchem.2021.23004.