Cahyono, H., W. T. Subroto, and K. Anwar. “Income Disparity in Gerbangkertosusila Area of East Java Indonesia”. International Journal of Economics and Financial Issues, vol. 7, no. 1, Jan. 2017, pp. 14-18, https://www.econjournals.com/index.php/ijefi/article/view/2868.