1. European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Geel, Belgium
2. Department of Biochemistry, Faculty of Medicine, University of Szeged, Szeged, Hungary
3. European Commission, Joint Research Centre, Institute for Health and Consumer Protection, Ispra, Italy
4. European Commission, Directorate-General for Research, Health Biotechnology, Brussels, Belgium
5. QualiCont Kht., Szeged, Hungary