1. Institute of Mathematics “Simion Stoilow” of the Romanian Academy, P.O. Box 1-764, 014700 Bucharest, Romania
2. Cambridge Cancer Trials Centre, Department of Oncology, University of Cambridge, Addenbrookes Hospital, (P.O. Box 279) Hills Road, Cambridge CB2 0QQ, UK
3. MRC Biostatistics Unit Hub in Trials Methodology Research, University Forvie Site, Robinson Way, Cambridge CB2 0SR, UK
4. Department of Theoretical Physics and Informatics, University of Łódź, Pomorska 149/153, 90-236 Łódź, Poland