1. Unit of Biostatistics, IRCCS “Casa Sollievo della Sofferenza”; San Giovanni Rotondo (FG) Italy
2. Department of Medical Sciences, Division of Internal Medicine and Chronobiology Unit, IRCCS “Casa Sollievo della Sofferenza”; San Giovanni Rotondo (FG) Italy
3. School of Mathematical Sciences; University of Nottingham; Nottingham U.K.
4. Unit of Biostatistics, DPCE; Consorzio Mario Negri Sud; Santa Maria Imbaro (CH) Italy