Niknam K, Sajadi SA, Hosseini R, Baghernejad M. Silica-bonded n-propyldiethylenetriamine sulfamic acid as a recyclable solid acid catalyst for the synthesis of coumarin and biscoumarin derivatives. Iran. J. Catal. 2024 Feb. 3;4(3). Available from: https://oiccpress.com/ijc/article/view/3806