Shafqat, Syed Salman, Amir Azam Khan, Misbahul Ain Khan, Shanti Faridah Salleh, Mohd Syahmi Jamaludin, and Pang Suh Cem. 2016. “Green Synthesis and Characterization of 3-Carboxycoumarin and Ethylcoumarin-3-Carboxylate via Knoevenagel Condensation”. Asian Journal of Chemistry 29 (2):261-66. https://doi.org/10.14233/ajchem.2017.20142.