1. Crippa Vein Clinic, Private Practice, Como, Italy
2. Vascular Diseases Center, University of Ferrara, Ferrara, Italy
3. Zini Vein Clinic, Private Practice, Parma, Italy
4. Tessari Studi, Private Practice, Verona, Italy
5. Department of Physics and Earth Sciences, University of Ferrara, Ferrara, Italy
6. Department of Medical Sciences, Center for Clinical Epidemiology, University of Ferrara, Ferrara, Italy
7. Department of Surgery, Uniformed Services University of the Health Sciences, Bethesda, MD, USA