Azimi SC, Kefayati H. Cellulose sulfuric acid: an efficient biopolymer-based catalyst for the synthesis of 5H-dibenzo[b,i]xanthene-tetraones and spiro[dibenzo[b,i]xanthene-13,3′-indoline]-pentaones under solvent free conditions. Iran. J. Catal. 2024;3(3). Accessed May 19, 2026. https://oiccpress.com/ijc/article/view/3763