’This volume in the series ‘’The International Library of Critical Writings in Economics’’, is an essential reference source for researchers, containing a selection of most important and pioneering articles written by the most outstanding experts in the field. . . . Certainly, it is a benefit to economists to have all these path-breaking papers from widely scattered sources brought together conveniently. Such papers represent the progress of research, which already looks impressive. The volume will be an important stimulus to further research as well.’- Elettra Agliardi, The Economic Journal