1. 1. Van Gelder HM, Allen KB, Renz B, Sherman R. Spontaneous pneumoperitoneum. A surgical dilemma. Am Surg 1991; 57: 151-6.
2. 2. Mularski RA, Ciccolo ML, Rappaport WD. Nonsurgical causes of pneumoperitoneum. West J Med 1999; 170:41-46.
3. 3. Volker R. Jacobs, Christoph Mundhenke, Nicolai Maass, Felix Hilpert, Walter Jonat. Sexual Activity as Cause for Non-Surgical Pneumoperitoneum. JSLS 2000; 4:297-300
4. Pneumoperitoneum without perforation of gastrointestinal tract;Omori;Dig Surg,2003
5. Pneumoperitoneum: a review of nonsurgical causes;Mularski;Crit Care Med,2000