Humphries, S. C., A. Burns, and T. Tanaka. “‘My Head Became Blank and I couldn’t speak’: Classroom Factors That Influence English Speaking”. The Asian Journal of Applied Linguistics, vol. 2, no. 3, Dec. 2015, pp. 164-75, https://caes.hku.hk/ajal/index.php/ajal/article/view/230.