This free course was written by Martin Pennington.
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Figure 1: Globe in Flickr made available under Creative Commons Attribution-ShareAlike 2.0 Licence.
Figure 2: Parliament in Flickr made available under Creative Commons Attribution 2.0 Licence.
Figure 3: © annatodica/iStockphoto.com
Figure 4: U.S. Department of Agriculture in Flickr made available under Creative Commons Attribution 2.0 Licence.
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