Azman Ong, M. H., and Z. Mahmud. “An Exploratory Factor Analysis of Market Survey Instruments for Automobile Industry: A study on Malaysian Motor Vehicle Industry”. Thailand Statistician, vol. 18, no. 4, Sept. 2020, pp. 481-90, https://ph02.tci-thaijo.org/index.php/thaistat/article/view/242041.