Patrick Ion; Robert Miner. <a href="http://www.w3.org/1999/07/REC-MathML-19990707"><cite>Mathematical Markup Language (MathML) 1.01 Specification.</cite></a> 7 July 1999. W3C Recommendation. URL: <a href="http://www.w3.org/1999/07/REC-MathML-19990707">http://www.w3.org/1999/07/REC-MathML-19990707</a>