1. University Clinic of Gastroenterohepatology, Faculty of Medicine, University “Ss. Cyril and Methodius”, Skopje, Macedonia (the former Yugoslav Republic of)
2. University Clinic of Gastroenterohepatology, Faculty of Medicine, University “Ss. Cyril and Methodius”, Skopje, Mecedonia (the former Yugoslav Republic of)
3. Research Center for Genetic Engineering and Biotechnology “Georgi D. Efremov”, Macedonian Academy of Sciences and Arts, Skopje, Macedonia (the former Yugoslav Republic of)
4. Institute of Epidemiology and Biostatistics, Faculty of Medicine, University “Ss. Cyril and Methodius”, Skopje, Macedonia (the former Yugoslav Republic of)
5. Macedonian Academy of Sciences and Arts, Skopje, Macedonia (the former Yoguslav Repyblic of)