Como extrair a fonte da imagem de uma string rss

This is the yahoo news rss feed
<p><a href="http://us.rd.yahoo.com/dailynews/rss/us/*http://news.yahoo.com/s/ap/20110521/ap_on_re_us/us_michelle_obama_west_point"><img src="http://d.yimg.com/a/p/ap/20110520/capt.53a8af4c675f421c8b7cba014c589d29-53a8af4c675f421c8b7cba014c589d29-0.jpg?x=130&y=97&q=85&sig=iOyBvkyg0rEKSK3hjlSsNA--" align="left" height="97" width="130" alt="First lady Michelle Obama, left, and Lt. Gen. David Huntoon, superintendent at the U.S. Military Academy, arrive in Washington Hall for a graduation banquet, Friday, May 20, 2011, in West Point, N.Y. (AP Photo/Mike Groll)" border="0" /></a>AP - First lady Michelle Obama urged more than 1,000 cadets Friday night on the brink of graduating to keep in mind the families of the soldiers they will lead.</p><br clear="all"/>

how posso extrair a fonte da imagem (http://d.yimg.com/a/p/ap/20110520/capt.53a8af4c675f421c8b7cba014c589d29-53a8af4c675f421c8b7cba014c589d29-0.jpg) desta strin

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