Every effort has been made to ensure that the contents of these WWW pages are up to date and factually correct. However, the NPG Group cannot guarantee that errors will not occur. The group apologises for any inconvenience that mistakes may cause and would be grateful if readers inform us of these.

A footnote to every page includes the date the contents of that page were last updated and contact details of the person responsible for that page. Queries and comments should be sent to the person responsible for the page.

This page last updated on 15th April 1997 by I.Thompson@ph.surrey.ac.uk.