In the Fall of 1975, owing to an affluence of visitors to the Computing Center of the Polish Academy of Sciences, 'the Group of Mathematical Jvlethods in Economics organized a series of seminars on topics related to mathematics and economics. Some of the visitors were supported by an exchange program, some come as guests of the Center and others come as our private guests. This volume presents some of the contributions to those seminars. The editors gratefully acknowledge the patience and efforts of the individual authors in the preparation of this volume. Among those who delivered lectures in the seminar series, apart from contributors to this volume, were L. Bauer from the Hochschule fur Welthandel in Vienna, S. A. Ivankov and S. M. Movschovich from Central Institute of Economics and Mat- matics in Moscow and P. Serafini and W. Ukowicz from the University of Trieste. They contributed much to the success of the meeting~. The permanent staff of the Group did most of the organizing work. The editors would like to express their gratitude to the direc tors of the Computing Center, R. Kulikowski, Z. Pawlak and Z. Szoda for their help and suggestions and to Mrs C. G6ralowa for help in administrative matters. Jerzy l. os Maria W. l. os Andrzej Wieczorek Contents C. Ballarini and O. liIIoeschlin, An open von Neumann model with consumption . . . 1 T.

Inhalt
An open von Neumann model with, consumption.- Contribution to the theory of existence of von Neumann equilibria (II).- Cournot-Bertrand mixed oligopolies.- La grange multipliers for the problem of stochastic programming.- Von Neumann models defined by transformations and by production cones.- Von Neumann models of open economies.- Reswitching of techniques and equilibria of extended von Neumann models.- Quasi-Leontief models.- Coalition games without players. An application to Walras equilibria.- The outline of a general disequilibrium dynamic model with personal income and wealth distributions.