Keyuravong, S., D. Seyitkuliyev, and T. Bunsom. “Investigation of Grammatical Errors Committed by Turkmen Learners of English”. Journal of Humanities and Social Sciences University of Phayao, Vol. 8, no. 1, Aug. 2019, pp. 96 - 117, https://so03.tci-thaijo.org/index.php/Humanties-up/article/view/205275.