Niknam, K.; Sajadi, S. A.; 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, 4 (3).