Acknowledgements
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Grateful acknowledgement is made to the following sources for permission to reproduce material in this course:
Course image: chiaralily in Flickr made available under Creative Commons Attribution-NonCommercial 2.0 Licence.
The material acknowledged below contains Proprietary content which is used under licence (not subject to Creative Commons licence). See Terms and conditions.
This extract is taken from K202 produced by the BBC on behalf of the Open University © 1999 The Open University
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