execuse me, how can I get the zip.xsl file

when I watch some demos with expath-zip, I see code like that :
<xsl:import href="http://expath.org/ns/zip.xsl"/>
or
<xsl:import href="http://www.expath.org/mod/zip.xsl"/>
. 
The problem is how can I get the zip.xsl file, these href are unavailable。
thank you very much
