Narayanaswamy Venugopala, K. et al. 2013. Trifluoroacetic Acid: An Efficient Catalyst for Paal-Knorr Pyrrole Synthesis and Its Deprotection. Asian Journal of Chemistry. 25, 15 (Sep. 2013), 8685–8689. DOI:https://doi.org/10.14233/ajchem.2013.15185.