http://www.cs.unibo.it/babaoglu/courses/security/documents/harrison-ruzzo-ullman.pdf
For discussion of this paper on the e-lang mailing list, see http://www.eros-os.org/pipermail/cap-talk/2004-May , for example http://www.eros-os.org/pipermail/cap-talk/2004-May/001649.html .