I have an XML document I generate on the fly, and I need a function to eliminate any duplicate nodes from it.

My function looks like:

declare function local:start2() {
    let $data := local:scan_books()
    return <books>{$data}</books>
};

Sample output is:

<books>
  <book>
    <title>XML in 24 hours</title>
    <author>Some Guy</author>  
  </book>
  <book>
    <title>XML in 24 hours</title>
    <author>Some Guy</author>  
  </book>
</books>

I want just the one entry in my books root tag, and there are other tags, like say pamphlet in there too that need to have duplicates removed. Any ideas?

Updated following comments. By unique nodes, I mean remove multiple occurrences of nodes that have the exact same content and structure.