UNIVERSITY OF WROC£AW
 WROC£AW UNIVERSITY OF SCIENCE AND TECHNOLOGY
 GENERAL INFORMATION PROBABILITY AND MATHEMATICAL STATISTICS is published by the Kazimierz Urbanik Center for Probability and Mathematical Statistics, and is sponsored jointly by the Faculty of Mathematics and Computer Science of University of Wroc³aw and the Faculty of Pure and Applied Mathematics of Wroc³aw University of Science and Technology. The purpose of the journal is to publish original contributions to the theory of probability and mathematical statistics. Probability and Mathematical Statistics was founded in 1980 and its establishment was a result of the initiative of the Wroc³aw probability community led by Kazimierz Urbanik and Czes³aw Ryll-Nardzewski, and statistics community represented by Witold Klonecki. They served as Editors of the journal during the first twenty-five years of its existence, with Urbanik shouldering the role of the Editor-in-Chief. Beginning with 2007, PMS became an affiliated journal of the Institute of Mathematical Statistics (IMS), San Francisco, CA. PMS (ISSN 0208-4147) is indexed by Scopus, Index Copernicus and Journal Citation Reports (2019 IF=0.617). PMS is an open access journal. All papers are refereed. Decisions on acceptance of papers are made by the Editorial Board. Manuscripts should be prepared in LaTeX and submitted as pdf files to PMS Editorial System All other correspondence concerning PMS should be sent to the email address pms@math.uni.wroc.pl PROBABILITY AND MATHEMATICAL STATISTICS is published in one volume (2 issues) a year. Orders for subscriptions and back fascicles should be addressed to: Publications Department Institute of Mathematics Polish Academy of Sciences ul. Sniadeckich 8 00-656 Warszawa, Poland e-mail: zadrozny@impan.pl Fax: (48-22) 6293997 https://www.impan.pl/en/publishing-house/journals-and-series EU VAT no: PL 525 000 88 67 Beginning with volume 20, the price per volume (two issues) is U.S. $60 including postage and handling, and the price of a single issue - U.S.$ 30. Air mail postage rates are available upon request. ISSN 0208-4147