Thomas, Abhilash, et al. “ASSESSMENT OF PSYCHOLOGICAL STRESSORS OF DEPRESSION AND ANXIETY USING DEPRESSION ANXIETY STRESS SCALE-21 IN SOUTH INDIAN HEALTHY VOLUNTEERS”. International Journal of Pharmacy and Pharmaceutical Sciences, vol. 8, no. 5, May 2016, pp. 288-95, https://www.journals.innovareacademics.in/index.php/ijpps/article/view/11212.