The essays in this volume were presented to Professor Isamu Yamada in honor of his seventy-third birthday. In view of his many professional contributions and associations, a single volume of essays is really insufficient to house the works of all those who wish to be part of a venture of this kind. Therefore, the editors would like to apologize to those friends and well-wishers of Professor Yamada who could not be accommodated in this volume. Born in Nagoya in 1909, Professor Yamada began his brilliant career at Nagoya Commercial College where he studied economics, statistics, mathematics and...