1. Europainclinics, Prague, Czech Republic
2. Europainclinics, Nové Mesto, Slovak Republic
3. Europainclinics, Bardejov, Slovak Republic
4. Clinic of Anaesthesiology and Intensive Care Medicine, East Slovak Institute of Cardiovascular Disease, Košice, Slovak Republic
5. Europainclinics, Poliklinika Terasa, Košice, Slovak Republic
6. Clinic of Anaesthesiology and Intensive Care Medicine, Railway Hospital and Clinic Košice, Košice, Slovak Republic
7. Wirbelsäuleninstitut, Munich, Munich, Germany
8. Kent Institute of Medicine and Surgery, Kent, UK
9. Department of Neurosurgery, Faculty of Medicine, Pavol Jozef Šafárik University in Košice, and Louis Pasteur University Hospital, Košice, Slovak Republic
10. Department of Medical and Clinical Biochemistry, Faculty of Medicine, Pavol Jozef Šafárik University in Košice, Košice, Slovak Republic