1. A thousand operations for ulcer disease;Welch;Ann Surg,1986
2. Morbidity and mortality of perforated peptic gastroduodenal ulcer following emergency surgery;Kujath;Langenbeck’s Arch Surg,2002
3. Gastro-duodenal peptic ulcer perforation;Dakubo;East Afr Med J,2009
4. Perforated peptic ulcer - an update;Chung;World J Gastrointest Surg,2017
5. Wells G.A., Shea B., O’Connell D., et al. “The Newcastle-Ottawa Scale (NOS) for assessing the quality of nonrandomised studies in meta-analyses - Coding Manual.” Pages 2-4. Ottawa Hospital Research Institute. University of Ottawa. Accessed April 29, 2020. http://www.ohri.ca/programs/clinical_epidemiology/oxford.asp#.Xqka48TcRiM.email.