<h1 id="ref-540">REF-540</h1> <ul> <li>Title: Usability of Security: A Case Study</li> <li>Author: ['J. D. Tygar', 'Alma Whitten']</li> <li>Time: 19981215</li> <li>URL: http://reports-archive.adm.cs.cmu.edu/anon/1998/CMU-CS-98-155.pdf</li> </ul>