<p>To provide a complete reference while minimizing the amount of work:</p>

<ul>
<li>For papers that have a DOI, always link to <a href="http://dx.doi.org/thisisthedoi" rel="nofollow">http://dx.doi.org/thisisthedoi</a>.  Otherwise, link to the publisher's page for the paper, or some other source that provides a full citation and (if available) a link to the PDF.</li>
<li>Clicking on the link will give the reader a full citation, so providing the full citation (author, title, journal, etc.) in the answer should not be required.</li>
<li>Optionally, add a second link with the text “(PDF)”.  This link should be to a free verison.</li>
<li>We shouldn't <em>expect</em> the answerer to dig up a link to a free PDF.  Given a full citation, it is not too hard for the reader to Google for that himself if he doesn't have access to the publisher's version through his institution's library.  It's ok to offer a link to a free PDF in a comment.</li>
<li>Incorporate the link into the answer informally, in whatever way makes sense.</li>
<li>If you want to include a full citation, feel free, but I don't think it's necessary to prescribe a format.</li>
</ul>

<p>Examples of fine ways to incorporate links:</p>

<ul>
<li><p>“If you use <a href="http://nips.cc/Conferences/2008/Program/event.php?ID=1258" rel="nofollow">random kitchen sinks</a> (<a href="http://books.nips.cc/papers/files/nips21/NIPS2008_0885.pdf" rel="nofollow">PDF</a>), you can …”</p></li>
<li><p>“Boosting seems to work well for <a href="http://dx.doi.org/10.1093/bioinformatics/btm497" rel="nofollow">protein subcellular localization patterns</a> and <a href="http://dx.doi.org/10.1073/pnas.0808843106" rel="nofollow">cellular morphologies</a>.”</p></li>
<li><p>“You may want to try <a href="http://dx.doi.org/10.1109/TMI.2008.918329" rel="nofollow">Cheeger regularization</a>.”</p></li>
<li><p>“<a href="http://dx.doi.org/10.1214/aos/1016218223" rel="nofollow">Friedman, Hastie and Tibshirani</a> show that boosting can be understood as additive logistic regression.”</p></li>
</ul>
