1. B. Geerts E. Linacre Changes in Concentration of Atmospheric Carbon Dioxide, other Greenhouse Gases, and Aerosols http://www-das.uwyo.edu/∼geerts/cwx/notes/chap01/co2_change.html 2002
2. Changes in Rainwater pH associated with Increasing Atmospheric Carbon Dioxide after the Industrial Revolution
3. Organisation for Economic Co-operation and Development (OECD) OECD Environmental Outlook to 2030 Organization for Economic Cooperation and Development 2008
4. V. Ishler Agriculture's Contribution to Greenhouse Gas Emissions: “In Perspective” http://blogs.das.psu.edu/tetherton/2007/10/17/agricultures-contribution-to-greenhouse-gas-emissions-in-perspective/ 2007