Among unconventional agents and unclassified viruses the contributions to this volume focused on prion-related diseases, with special emphasis on bovine spongiform encephalopathy and human spongiform encephalopathies, and Borna disease virus, an agent known since long time to be pathogenic for horses and sheep, which is now discussed as a potential pathogen for humans. Additionally, the volume contains articles about newly discovered viruses like porcine respiratory and reproductive syndrome virus and viruses that are classified only provisionally like African swine fever virus, hepatitis C and E viruses, or the arteriviruses.

We wish to thank Georg Hasenkamp for valuable comments on an earlier draft of the manuscript and Steven Diamond for his kindness in reading the manu script and providing advice regarding the style of the exposition. We are also grateful to Miss Ingeborg Kasper for her careful typing of the manu script. Contents 1. Introduction 4 2. Price Indices Depending only on Prices 2. 1 Definition, Examples, Implications 4 2. 2 Characterizations of Pri e Indices 15 3. Price Indices Depending on Prices and Quantities 22 3. 1 Definition, Examples 23 3. 2 Fisher's System of Tests 29 3. 3 Implications and Characterizations 35 3. 4 Independence and Inconsistency of Fisher's Tests 44 3. 5 General Solution of the Inconsistency Problem 54 4. Price Levels, Price Indices, and Fisher's Equation 59 of Exchange 4. 1 Definition, Examples, Implications 60 4. 2 Characterizations of Price Levels 64 4. 3 Fisher's Equation of Exchange Reconsidered 72 Bibliography 5. 83 6. Index 88 1. Introduction In the face of the economic, political, and social problems resul ting from world-wide inflation, theories of the price index have gained new attention. This newfound interest in price indices stems from the fact that all such indices are designed to serve as yardsticks for measuring the price behavior of goods and services. That is, all price indices relate to the concept of the 'purchasing power of money'. If prices increase, then the value of the unit of money declines, i. e."

The first of its kind, a seminar on Production Theory was held at the University of Karlsruhe during May and June 1973. Seven of the nineteen resource participants were from Canada, France, the Netherlands, Sweden and the U.S.A., to make the seminar an international symposium. The other par- ticipants involved a variety of experts from German univer- sities. Karlsruhe supplied the predominant part of the Ger- man contributors. For the discussions of the seminar twenty papers span- ning a large part of production theory were prepared and these papers are herewith published as a coherent collection under the title: KARLSRUHE SEMINAR ON PRODUCTION THEORY. Papers on scalar valued production functions are orga- nized in Part 1. Several of these provide new characteri- zations of CES productiop functions, partly in connection with technical progress, and two others are related to homothetic production functions. Six papers on multisectoral production models have been included in Parts 2 and 3, addressed in part to problems of dynamic structures, disaggregation and relaxation of simple homogeneity. Turning next to more general production models, Part 4 contains five papers involving set valued production func- tionsor production correspondences, dealing with such topics as efficient pOints, stochastic aspects, homogeneity, homo- theticity and the law of diminishing returns.