J. A. Wahab, N. F. Mohamad Razi, M. M. H. Mohammad Hamzah, A. Z. Azmi, and N. H. Nasrudin, “Measuring Anxiety Level of Failure Science Students in Performing Calculus Subject”, IJET, vol. 7, no. 4.33, pp. 74–77, Dec. 2018, doi: 10.14419/ijet.v7i4.33.23489.