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Hi, As far as I know this is not possible, also the answer/ question you mentioned doesn't speak about including multiple sitemap indexes within a sitemap index. He's referring to multiple sitemaps within a sitemap index which is of course very normal. As also mentioned within the error section of the Google Webmaster Help part about the Sitemaps: http://support.google.com/webmasters/bin/answer.py?hl=en&answer=35738 there's an related error to this: Incorrect Sitemap index format: Nested Sitemap indexes. Hope this helps!