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Wikipedian artikkeli englanniksi http://en.wikipedia.org/wiki/Photovoltaicshttp://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VPK-42JHDHD-2G&_user=8758023&_coverDate=02%2F06%2F2001&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1398591133&_rerunOrigin=google&_acct=C000071355&_version=1&_urlVersion=0&_userid=8758023&md5=ad3072d962e393af83f9fbc4653ebfaf