The Prague Conferences on Information Theory, Statistical Decision Functions, and Random Processes have been organized every three years since 1956. During the eighteen years of their existence the Prague Conferences developed from a platform for presenting results obtained by a small group of researchers into a probabilistic congress, this being documented by the increasing number of participants as well as of presented papers. The importance of the Seventh Prague Conference has been emphasized by the fact that this Conference was held jointly with the eighth European Meeting of Statisticians. This joint meeting was held from August 18 to 23, 1974 at the Technical University of Prague. The Conference was organized by the Institute of Information Theory and Automation of the Czechoslovak Academy of Sciences and was sponsored by the Czechoslovak Academy of Sciences, by the Committee for the European Region of the Institute of Mathematical Statistics, and by the International As sociation for Statistics in Physical Sciences. More than 300 specialists from 25 countries participated in the Conference. In 57 sessions 164 papers (including 17 invited papers) were read, 128 of which are published in the present two volumes of the Transactions of the Conference. Volume A includes papers related mainly to probability theory and stochastic processes, whereas the papers of Volume B concern mainly statistics and information theory."

The Prague Conferences on Information Theory, Statistical Decision Functions, and Random Processes have been organized every three years since 1956. During the eighteen years of their existence the Prague Conferences developed from a platform for presenting results obtained by a small group of researchers into a probabilistic congress, this being documented by the increasing number of participants as well as of presented papers. The importance of the Seventh Prague Conference has been emphasized by the fact that this Conference was held jointly with the eighth European Meeting of Statisticians. This joint meeting was held from August 18 to 23, 1974 at the Technical University of Prague. The Conference was organized by the Institute of Information Theory and Automation of the Czechoslovak Academy of Sciences and was sponsored by the Czechoslovak Academy of Sciences, by the Committee for the European Region of the Institute of Mathematical Statistics, and by the International As sociation for Statistics in Physical Sciences. More than 300 specialists from 25 countries participated in the Conference. In 57 sessions 164 papers (including 17 invited papers) were read, 128 of which are published in the present two volumes of the Transactions of the Conference. Volume A includes papers related mainly to probability theory and stochastic processes, whereas the papers of Volume B concern mainly statistics and information theory."

The Ninth Prague Conference on Information Theory, Statistical Decision Functions, and Random Processes was organized by the Institute of Information Theory and Automation of the Czechoslovak Academy of Sciences from June 28 to July 2, 1982. Similarly as the preceding Prague Conferences, during their twenty six years histo ry, it provided a space for the presentation and discussion of recent scientific results, as well as for personal contacts of many scien tists both from abroad and from Czechoslovakia. Nearly 150 special ists from 17 countries participated in the Conference and they read more than 100 papers (including 18 invited ones), 88 of which have been published in the present two volumes of the Transactions of the Conference. Namely invited papers, having been read by outstanding specialists, have brought invaluable offer for participants to create themselves an orientation in the modern trends of the above mention ed scientific branches. Allow us to use this opportunity to express our sincere thanks to all who have contributed to the success of the Conference, espe cially to those who prepared and presented papers. Our gratitude is also due to Academician Jaroslav Kozesnik, the scientific editor of the Transactions, and to the editorial board for reviewing all papers and fulfilling many printing manage ment duties. We would like to appreciate a great work of all colleagues from the Institute of Information Theory and Automation, who participated in the preparation and in the organization of the Conference."

During the past Prague Conferences, the Organizing Committee had to face with a great regret permanent and even increasing delays in publishing the Transactions. The delays seemed to be out of any our reach as long as the traditional manuscript delivery rules and traditional printing technique were supposed to be employed. This is why we decided, starting with this Conference, for a new method of papers collection and printing. We want to thank all participants of our conference, in particular those who contributed to the volu- mes A and B, for understanding this our step. Our thanks are due to Academician Jaroslav Koieinik, the scien- tific editor of these volumes, and to the editorial board for re- viewing all papers and fulfiling many printing management duties. We also thank Academia Publishing House for printing the whole volume in time. ORGANIZING COMMITTEE of the EIGHTH PRAGUE CONFERENCE on INFORMATION THEORY, STATISTICAL DECISION FUNCTIONS, RANDOM PROCESSES PROBLEMES LIES A LA DETERMINATION DES SPECTRES DE PUISSANCE EN THEORIE DES FONCTIONS ALEATOIRES A. Blanc-Lapierre Gif-sur-Yvette (France) ~ La dll!termination exp~rimentale du spectre de pui,ssance, au sens physique, d'une grandeur fluctuante pose des probl~mes' d'analyse spectrale et d'ergodisme. Ces deux types de probl~mes sont examin~s conjointement pour une grandeur repr~sent~e par une fonction al~atoire X(t,~), pas n~cessairement stationnaire, mais pr~sentant des caract~res de permanence suffisants pour que la puissance moyenne puisse @tre difinie.