How this tutorial is presented Sequentially The tutorial is intended to be followed through sequentially, however, readers may return to the menu page and jump to a particular section of the presentation from any page. Using some supplementary external links Where appropriate links to external pages are provided to supplement the tutorial. These links are provided in good faith and with the exception of EC related sites only link to home pages. If you have any comments about these links please contact Robert Pitkethly. Providing sources for further information The tutorial concludes with a selection of further reading and sources of further information. With a download option as a Microsoft Word document or as an Adobe Acrobat .pdf file