Google Sitemap generation - double links

Hello fellow ZMs users,

I'm generating a Google sitemap using the code from http://www.zms-publishing.com/dokumentation/howto/import_export_xml/google_sitemaps/index_ger.html. 
This works fine until I noticed that some folders are in there twice:

<url>
<loc>/index_ger.html</loc>
<lastmod>2012-01-26</lastmod>
<changefreq>daily</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>/klinik/willkommen/index_ger.html</loc>
<lastmod>2011-03-09</lastmod>
<changefreq>daily</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>/klinik/willkommen/index_ger.html</loc>
<lastmod>2011-07-28</lastmod>
<changefreq>daily</changefreq>
<priority>0.5</priority>
</url>
<url>
<loc>/klinik/klinikdirektion/index_ger.html</loc>
<lastmod>2011-07-28</lastmod>
<changefreq>daily</changefreq>
<priority>0.5</priority>
</url>

Any ideas how this could happen?

Best, Sebastian Tänzer

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