Ertugrul, Mustafa Emre, and Kemaletttin Tanrıseven. “Analysis of Income Convergence in G-20 Countries With Structural Break Unit Root Test”. International Journal of Economics and Financial Issues, vol. 8, no. 2, Mar. 2018, pp. 344-9, https://econjournals.com/index.php/ijefi/article/view/6453.