TY  - RPRT
TI  - Upper gastrointestinal endoscopy.
AU  - W G Guilford
PY  - 1990
DO  - 10.1016/s0195-5616(90)50301-0
UR  - https://pubmed.ncbi.nlm.nih.gov/2238368/
ID  - 2238368
ER  -