The echocardiographic assessment of pulmonary artery pressure and pulmonary vascular resistance.Stephen S. Hirschfeld, Samuel Kaplan, J Kofhagen et al.|Circulation|1975Cited by 193
Measurement of right and left ventricular systolic time intervals by echocardiography.Stephen S. Hirschfeld, Samuel Kaplan, Joan Korfhagen et al.|Circulation|1975Cited by 171
Persistence of fetal circulation syndrome: An echocardiographic studyThomas W. Riggs, Connie Bormuth, Stephen S. Hirschfeld et al.|The Journal of Pediatrics|1977Cited by 52
Aortic valve replacement in childhood: Evaluation of left ventricular function by electrocardiography, echocardiography and graded exercise testingGeorge S. Bisset, Samuel Kaplan, David C. Schwartz et al.|The American Journal of Cardiology|1983Cited by 9