This course was written by Lindsay Hewitt and Sarah Burton, with quizzes by Julie Robson.

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Figure 1: Ross Finnie for © The Open University

Figure 2: Badge illustration © The Open University

Figure 4: © Revensis/

Figures 5 and 6: courtesy of Sarah Burton for The Open University

Figure 7: © Marek Uliasz/Dreamstime

Figure 11: © Logorilla/

Figure 12: courtesy of Sarah Burton for The Open University

Figure 14: Gill Ryan for © The Open University

Figure 15: © Globalstock/

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