Usman, Ahmad, et al. “NORMAL CORONARY ANGIOGRAMS IN PATIENTS OF SUSPECTED CORONARY ARTERY DISEASE: A SIX YEAR STUDY AT ARMY CARDIAC CENTRE LAHORE”. Pakistan Armed Forces Medical Journal, vol. 71, no. 1, Feb. 2021, pp. 117-21, https://pafmj.org/PAFMJ/article/view/6360.