1. Institute of Biology and Immunology of Reproduction-BAS, bul. Tsarigradsko Shose 73, p.c. 1113, Sofia, Bulgaria
2. Institute of Biology and Immunology of Reproduction- BAS, bul. Tsarigradsko shose 73, p.c. 1113, Sofi a, Bulgaria
3. Agricultural Institute, BG – Turgovishte, Bulgaria