AL-Rawi, Y. A. ., Imlus, M. H. ., Yusup, Y. . and Yahya, S. B. . (2018) “The Optimal Progressive Tax Policy to Reduced Vehicles Externalities”, Journal of Asian Scientific Research, 8(8), pp. 265–276. doi: 10.18488/journal.2.2018.88.265.276.