This free course was written by Tom Redshaw, Bedford College Group using materials belonging to The Open School Trust Ltd. (trading as the National Extension College), in partnership with Middlesbrough College, West Herts College and The Open University and in collaboration with Coleg Cambria, Adult Learning Wales, Coleg Gwent and the NPTC Group of Colleges. Copyright in this material belongs to The Open University, 2019.
Except for third party materials and otherwise stated (see terms and conditions [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] ), this content is made available under an Open Government Licence.
Grateful acknowledgement is made to the following sources for permission to reproduce material in this free course:
219680: Figure 1 bottom left: © michael spring / 123 Royalty Free
219600: Figure 1 bottom right: © SolStock / istock / Premium Images Plus
219598: Figure 1 top left: © Katarzyna Bialasiewicz / 123 Royalty Free
219597: Figure 1 top right: © Bernard Bodo / 123 Royalty Free
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