1. Comenius University in Bratislava , Jessenius Faculty of Medicine in Martin, Martin University Hospital, Neurosurgery Clinic , Martin , Slovak Republic
2. Comenius University in Bratislava , Jessenius Faculty of Medicine in Martin, Biomedical Centre Martin , Martin , Slovak Republic
3. Comenius University in Bratislava , Jessenius Faculty of Medicine in Martin, Department of Pharmacology , Martin , Slovak Republic
4. Charles University Prague , 1st Medical Faculty, The Hospital Na Bulovce, The Ortopedic Clinic , Prague , Czech Republic