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2. USDA http://www.usda.gov/documents/USDA_Biofuels_Report_6232010.pdf 2010
3. Techno-economic analysis and life-cycle assessment of cellulosic isobutanol and comparison with cellulosic ethanol and n-butanol;Tao;Biofuels Bioprod Bioref,2013
4. Spake A http://www.america.gov/st/washfile-english/2007/September/20070919163628ndyblehs0.6094019.html