Butterworth-Heinemann Linacre House, Jordan Hill, Oxford OX2 8DP 225 Wildwood Avenue, Woburn, MA 01801-2041 A division of Reed Educational and Professional Publishing Ltd A member of the Reed Elsevier group plc First published by Macmillan Education Ltd 1981 Second edition 1985 Third edition 1988 Fourth edition published by Butterworth-Heinemann Ltd 1993 Reprinted 1994, 1996 Fifth edition 1997 Reprinted with revisions 1999 Sixth edition 2001 © David