Giap, Lim Soo, and Ong Sheau Fen. “The Effectiveness of Teaching Non-Native Learners in Recognizing the Differences of 4 Tones Using a Romanised Mandarin Web-Based Instruction”. Journal of Education and Vocational Research, vol. 1, no. 3, June 2011, pp. 67-71, https://doi.org/10.22610/jevr.v1i3.11.