<?xml version="1.0"?>
<dblp>
<article key="journals/dke/HoutsmaA91" mdate="2011-08-18">
<author>Maurice A. W. Houtsma</author>
<author>Peter M. G. Apers</author>
<title>Algebraic optimization of recursive queries.</title>
<pages>299-325</pages>
<year>1991</year>
<volume>7</volume>
<journal>Data Knowl. Eng.</journal>
<url>db/journals/dke/dke7.html#HoutsmaA91</url>
<ee>http://dx.doi.org/10.1016/0169-023X(92)90029-B</ee>
</article>
</dblp>
