Participants measure a grow lamp at the Gro Wholesale booth during the 2nd National Marijuana Business Conference and Expo in Auburn, Washington November 8, 2013. REUTERS/David Ryder (UNITED STATES - ... more 
Participants measure a grow lamp at the Gro Wholesale booth during the 2nd National Marijuana Business Conference and Expo in Auburn, Washington November 8, 2013. REUTERS/David Ryder (UNITED STATES - Tags: SOCIETY POLITICS DRUGS BUSINESS) less 
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Reuters | Photo By DAVID RYDER / REUTERS
Fri, Nov 8, 2013 8:58 PM EST