Meiza, A., S. Darwis, A. Y. Gunawan, and E. Fitriana. “Quantitative Analysis of Relationship Between Three Psychological Parameters Based on Swallowtail Catastrophe Model: A Recent Perspectives”. Theory and Applications of Mathematical Science Vol. 3, Mar. 2020, pp. 149-57, https://stm1.bookpi.org/index.php/tams-v3/article/view/1117.