1. Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
2. University Obstetrics and Gynecology Hospital “Maichin Dom”, 1431 Sofia, Bulgaria
3. Institute of Optical Materials and Technologies “Acad. Yordan Malinovski”, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
4. Department of Biochemistry, Medical University-Pleven, 5800 Pleven, Bulgaria