Luwaert, RJ., Cosyns, J.-P., Rousseau, MF., Brasseur, LA., Detry, JM., & Brohet, C. (1983). Reassessment of the Relation Between Qrs Forces of the Orthogonal Electrocardiogram and Left-ventricular Ejection Fraction. European Heart Journal (English Edition), 4(2), 103-109. https://hdl.handle.net/2078.5/67169 (Original work published 1983)