Kale, Mohan B., et al. “CuSCN Catalyzed Conjugate Addition of Grignard Reagents to Substituted Coumarins With Dilithium Tetrachloromanganate”. Asian Journal of Chemistry, vol. 32, no. 7, June 2020, pp. 1793-8, https://asianpubs.org/index.php/ajchem/article/view/2401.