@article{ref1,
title="Steel ball trick",
journal="Gastrointestinal endoscopy",
year="1975",
author="George, Jessica and Becker, M.",
volume="21",
number="4",
pages="176-177",
abstract="<p>[Abstract unavailable]</p><p>Language: en</p>",
language="en",
issn="0016-5107",
doi="",
url="http://dx.doi.org/"
}