1. L. J. Bernal, A. Montes, A. Bayon, M. J. Fdez.delPalacio, and C. Gutierrez panizo(1991 ) Evolucion del Electrocardio-grama en perros Beagles de 1 a 6 meses. XXIV Congreso Mundial de Veterinaria, Brasil.
2. G. Bolton(1975 ) Handbook of Canine Electrocardiography W. B. Saunders, Philadelphia, pp30 -58 .
3. The electrocardiogram of the normal dog