Dung, P., and T. Nguyen. “Synthesis of Pyrano[3,2-C]quinoline Derivatives Using Catalyst Prepared from L-Proline and P-Toluenesulfonic Acid”. Science & Technology Development Journal: Natural Sciences, Vol. 5, no. 3, May 2021, pp. 1275-83, doi:https://doi.org/10.32508/stdjns.v5i3.1008.