Hamid, Almas, et al. “Synthesis and Bioassay of Novel Phenylhydrazine and 2,4-Dinitrophenylhydrazine Substituted Carbazoles”. Asian Journal of Chemistry, vol. 25, no. 10, May 2013, pp. 5412-4, https://asianpubs.org/index.php/ajchem/article/view/7584.