Parveen, Sajida, et al. “ASSOCIATION OF AGE WITH HEMODYNAMIC RESPONSES TO THE HEAD-UP TILT TEST IN PATIENTS WITH VASOVAGAL SYNCOPE”. Pakistan Armed Forces Medical Journal, vol. 67, no. SUPPL-2, Apr. 2017, pp. S145-49, https://www.pafmj.org/PAFMJ/article/view/11893.