rssフィードの例を次に示します。
<item>
<title>Stem cells being made from blood</title>
<description>A patient's own blood has been used to make personalised stem cells, which doctors hope can be used to treat a range of diseases.</description>
<link>http://www.bbc.co.uk/news/health-20539835#sa-ns_mchannel=rss&ns_source=PublicRSS20-sa</link>
<guid isPermaLink="false">http://www.bbc.co.uk/news/health-20539835</guid>
<pubDate>Fri, 30 Nov 2012 00:45:53 GMT</pubDate>
<media:thumbnail xmlns:media="http://search.yahoo.com/mrss/" width="66" height="49" url="http://news.bbcimg.co.uk/media/images/64469000/jpg/_64469170_c0147104-red_blood_cells%2C_artwork-spl.jpg"/>
<media:thumbnail xmlns:media="http://search.yahoo.com/mrss/" width="144" height="81" url="http://news.bbcimg.co.uk/media/images/64469000/jpg/_64469171_c0147104-red_blood_cells%2C_artwork-spl.jpg"/>
media:thumbnailで.jpg画像のURLを取得する必要があります。xpathまたはxqueryでそれを行うにはどうすればよいですか?誰か助けてくれませんか?ありがとうございました!