In that we have duplicate audio book descriptions (author bio, story, praise...) for titles offered in more than one format (abridged, unabridged, compact disc, MP3 CD) I want to minimize the amount of "duplication" a search engine spider sees. Search Engine Watch says "One of the easiest ways to guarantee that you determine which copies of your content you want Google, Yahoo or Bing to index (if multiple versions exist on your site) is to specify the preferred URL version of the content in your sitemaps. This will ensure you control which version of the content you want search engines in general to index."
How do I specify preferred URLs in our sitemaps?