Pandey, R.N., et al. “Mononuclear Dioxomolybdenum(VI) and Dioxotungsten(VI) Complexes With Di(1-Phenyl Tetrazoline)-5,5’-Disulphie”. Asian Journal of Chemistry, vol. 7, no. 2, July 2012, pp. 285-8, https://asianpubs.org/index.php/ajchem/article/view/24284.