namespace question

Hi there,

I am not very familar with namespaces, so it would be nice if someone 
coult help me with the following simple example:

<unit xmlns="http://www.sdml.info/srcML/src">
	<namespace>
		<type_decl id="CB;" name="B" type="class">
		...
		</type>
	</namespace>
</unit>

This is part of the xml that is produced by srcML, a tool for converting 
Java to XML. As you can see srcML has its own namespace. My question is, 
how i can adress parts of the subtree with XPath from an XSLT 
Stylesheet. For example:

<xsl:copy-of select="/unit/namespace"/>

doesn't return anything. But if i delete the xmlns attribute the tree 
below "<namespace>" is returned.

Regards,
Garvin