A nuniber of changes have been made in Volume 7 of the series, and each volume
will henceforth be published in two paper-backed parts at approximately sixmonthly
intervals. On publication of the second part a complete volume will
become available in a single case-bound edition. We hope that the other minor
changes will also be appreciated by our readers.
As in previous volumes, we are grateful to reviewers and others for their
encouragement, criticisms and suggestions. We hope that the new arrangement
of six-nionthly issues wlll permit reviews to appear in print at a shorter interval
of time between submission and publication than has been achieved in the past.
Our thanks are due to the staff of Butterworths and to the authors, societies
and publishers for permission to use illustrations and tables.