@article{ref1,
title="A sequential procedure for teaching addition skills to trainable retarded students",
journal="Training school bulletin",
year="1972",
author="Brown, L. and Bellamy, T.",
volume="69",
number="1",
pages="31-44",
abstract="<p>[Abstract unavailable]</p><p>Language: en</p>",
language="en",
issn="0041-0918",
doi="",
url="http://dx.doi.org/"
}