Khojasteh, Laleh, et al. “SEMANTIC FUNCTIONS OF “OBLIGATION NECESSITY” AND‘VOLITION PREDICTION’ MODALS IN MALAYSIAN ENGLISH TEXTBOOKS:A CORPUS-BASED ANALYSIS”. International Journal of English and Education, vol. 3, no. 4, Oct. 2014, pp. 179-91, https://ijee.org/ijee/article/view/1018.