Mark Davis; Michael Everson; et al. <a href="http://www.unicode.org/unicode/reports/tr27/tr27-4.html"><cite>Unicode 3.1.0.</cite></a> 16 May 2001. Unicode Standard Annex #27. URL: <a href="http://www.unicode.org/unicode/reports/tr27/tr27-4.html">http://www.unicode.org/unicode/reports/tr27/tr27-4.html</a>