Acknowledgements

This session of the course was written by Anna Page on behalf of the Free Learning team at The Open University.

Images

Figure 1: John T. Spencer https://www.flickr.com/ photos/ edrethink/ 8731759135CC-BY-2.0

Every effort has been made to contact copyright owners. If any have been inadvertently overlooked, the publishers will be pleased to make the necessary arrangements at the first opportunity.