H. DING, O. JOKISCH, and R. HOFFMANN, “Perception and analysis of Chinese accented German vowels”, Arch. Acoust., vol. 32, no. 1, pp. 89–100, Mar. 2007, Accessed: Mar. 04, 2026. [Online]. Available: https://acoustics.ippt.gov.pl/index.php/aa/article/view/768