<xsl:include> element merges the contents of one stylesheet with another. Unlike the case of
<xsl:import>, the contents of an included stylesheet have exactly the same precedence as the contents of the including stylesheet.
<xsl:include href=URI />
- Specifies the URI of the stylesheet to include.
Top-level, may appear in any order as a child of
XSLT, section 2.6.1.