1. Wagner GS: Marriott's Practical Electrocardiography, ed 9. Baltimore, Williams & Wilkins, 1994, pp 79, 83, 96.
2. Mirvis DM: Electrocardiography. A Physiologic Approach. St. Louis, Mosby, 1993, p 304.
3. Grant's Clinical Electrocardiography, ed 2, rev Beckwith JR. New York, McGraw-Hill, 1970, p 121.
4. Macfarlane PW, Vetch Lawrie TD: Comprehensive Electrocardiography. New York, Pergamon, 1989, p 476.
5. Lipman BS, Dunn M, Massie E (eds): Clinical Electrocardiography, ed 7. Chicago, Year Book Medical Publishers, 1984, p 146.