K. Tyagi, Yogesh, Shvetambri Tyagi, Hanumantharao G. Raj, and Rajinder K. Gupta. 2010. “In Vitro Antioxidant Activity Evaluation of 4-Methyl Coumarin Derivatives”. Asian Journal of Chemistry 22 (5):3622-28. https://asianpubs.org/index.php/ajchem/article/view/11591.