You typically want this for source namespaces:
<xsl:transform xmlns:xsl='http://www.w3.org/1999/XSL/Transform' exclude-result-prefixes='m' xmlns:m='http://www.w3.org/1999/MathML" > <xsl:template match="m:math"> <p>Math is not supported</p> </xsl:template> </xsl:transform>