1. FAOSTAT 2010. http://faostat.fao.org (accessed on 22 February 2013).
2. Tobacco Board, http://tobaccoboard.com/admin/statisticsfiles/Exp_Perf_Currentyear.pdf (accessed on 27 June 2013).
3. F. Lowman, http://legacy.library.ucsf.edu/tid/wvj35e00 (accessed on August 30, 2013).
4. P. Morris, http://legacy.library.ucsf.edu/tid/rvj35e00 (accessed on August 30, 2013).
5. The Chemical Components of Tobacco and Tobacco Smoke;Rodgman,2013