1. http://www.esrl.noaa.gov/gmd/ccgg/trends/.
2. http://www4.unfccc.int/submissions/INDC/Submission%20Pages/submissions.aspx.
3. http://www.worldenergyoutlook.org/.
4. http://www.mitsubishielectric.com/news/2013/0326-a.html.
5. http://www.mitsubishielectric.com/news/2015/0622-a.html.