Awan, Z. A., M. Gallagher, E. Rowland, and A. Camm. “Flutter Wave Polarity on Sruface ECG and Endocardial Activation in Typical Counter Clockwise Atrial Flutter”. Journal of Postgraduate Medical Institute, vol. 18, no. 4, Oct. 2011, https://jpmi.org.pk/index.php/jpmi/article/view/951.