How to find all the List elements that contain a particular value using XPath and XSLT?

I'm not sure if this is an XSL or XPath question. It has to do with the type. In the schema I have...

a simple type:

   <xs:simpleType name="doubleListType">
     <xs:list itemType="xs:int" />
   </xs:simpleType>


I also have an element:
   <xs:element name="root">
     <xs:complexType>
       <xs:all>
         <xs:element name="Lists" minOccurs="0">
           <xs:complexType>
             <xs:sequence>
               <xs:element name="L" type="intListType" maxOccurs="unbounded"
/>
             </xs:sequence>
           </xs:complexType>
         </xs:element>
       </xs:all>
     </xs:complexType>
   </xs:element>

What I want is to be able to find all the List <L> elements that contain a particular value. I can seach for element values, but not values within a list. I would like to output this to XML, which I think, means I cannot use script commands, but I may be wrong there! Any help would be fantasic!!
You can do this with XSLT and XPath (which is embedded into XSLT) using something like this:

<xsl:template match="L">
         <xsl:value-of select="."/>
         <xsl:if test="test for value goes here">
                 <xsl:text>Output the number here</xsl:text>
         </xsl:if>
</xsl:template>