1. Breen WJ, Rekate AC (1960) Effect of posture on splitting of the second heart sound. JAMA 173: 106
2. Chandraratna PAN, Lopez JM, Cohen LS (1975) Echocardiographic observations on the mechanism of production of the second heart sound. Circulation 51: 292
3. Curtiss EI, Matthews R, Shaver JA (1975) Mechanism of normal splitting of the second heart sound. Circulation 51: 157
4. Curtiss EI, Shaver JA, Reddy PS, O’Toole JD (1975) Newer concepts in physiologic splitting of the second heart sound. in: Leon DF and Shaver JA (eds) Physiologic principles of heart sounds and murmurs. American Heart Association Monograph Series. American Heart Association, New York, Vol 46: 68
5. Ehlers KH, Engle MA, Farnsworth PB, Levin AR (1969) Wide splitting of the second heart sound without demonstrable heart disease. Am J Cardiol 23: 690