1. Department of Gastroenterology, General Hospital of Shenyang Military Area, Shenyang, China
2. Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, China
3. Department of Occupational and Environmental Health Sciences and the Ministry of Education Key Lab of Hazard Assessment and Control in Special Operational Environment, School of Public Health, Fourth Military Medical University, Xi'an, China
4. Library of Fourth Military Medical University, Xi'an, China