Dr. Prativa B. S. Dawadi, and Johan Lugtenburg. “Synthesis of Biologically Important Pyrrole Derivatives in Any 13C and 15N Isotope Enriched Form”. Global Journal of Science Frontier Research, vol. 12, no. B2, Jan. 2012, pp. 23-36, https://journalofscience.org/index.php/GJSFR/article/view/414.