Yu. K. Belyaev was a Professor Emeritus of Statistics at Umea University. He obtained a PhD from Steklov Mathematical Institute and a DSc from the Institute of Applied Mathematics, Academy of Sciences, USSR (supervisor A.N. Kolmogorov). He was deputy Chair of the Interfaculty Laboratory of Statistical Methods at Lomonosov Moscow State University, founded and led by A.N. Kolmogorov, and received the Nordbankens vetenskapliga and the USSR State Prize. His research focuses on stochastic processes, queueing theory, and mathematical statistics. He was a plenary speaker at various conferences; is a member of the editorial board of the journals Mathematical Methods of Statistics (USA) and Statistics (England); and an elected Member of the International Statistical Institute, the Institute of Mathematical Statistics, and the Swedish Statistical Society. A.H. Hajiyev is an academician of the Azerbaijan National Academy of Sciences. He obtained a PhD from Lomonosov Moscow State University and a DSc from Bauman Moscow State Technical University. He was awarded the Lenin Komsomol Prize in Science and Engineering and the Honorary Medal of the President of the Bulgarian Academy of Sciences; is a foreign member of the Moldova Academy of Sciences, a foreign member of the Georgian National Academy of Sciences and a foreign member of the Mongolian National Academy of Sciences. He is Honorary Professor, Chengdu University, China; a fellow of The World Academy of Sciences; an elected Member of the International Statistical Institute and an invited speaker at various conferences. He is a member of the Editorial Board of the international journals Applied and Computational Mathematics and Management Science and Engineering Management and co-editor of 16 books published by reputed publishers.