1. Physiologic and Pathologic Belching
Albert J. Bredenoord, André J.P.M. Smout 
Clinical Gastroenterology and Hepatology 
Volume 5, Issue 7, Pages (July 2007)
DOI: /j.cgh
Copyright © 2007 AGA Institute Terms and Conditions

2. Figure 1
Impedance tracings of gastric (left) and supragastric belching (right). During the gastric belch, air moves in proximal direction; during the supragastric belches, air enters the esophagus from proximal direction and is expelled immediately thereafter in retrograde direction.
Clinical Gastroenterology and Hepatology 2007 5, DOI: ( /j.cgh )
Copyright © 2007 AGA Institute Terms and Conditions