@article{ref1,
title="Effects of probability of reward and speed requirement on human performance",
journal="Journal of experimental psychology",
year="1963",
author="Zipf, S. G.",
volume="65",
number="",
pages="106-107",
abstract="<p>[Abstract unavailable]</p><p>Language: en</p>",
language="en",
issn="0022-1015",
doi="",
url="http://dx.doi.org/"
}