A. El-Essawy, Farag, and Safaa I.M. Rady. 2011. “Synthesis of Some N-Alkylated and 1,2,4-Triazole, 1,3,4-Oxa-, Thiadiazoles Containing 1H-Pyrazolo[3,4-b]pyridine Derivatives”. Asian Journal of Chemistry 23 (6):2461-67. https://asianpubs.org/index.php/ajchem/article/view/10462.