Musal B, Serin G, Tuna B. A Comparison of Ultrasonography and Measurement of Serum Progesterone Levels in the </strong><strong>Diagnosis of Postpartum OVarian Functional</strong><strong>Disturbances in Dairy Cows. Kafkas Univ Vet Fak Derg,  12 (1):  49-52,  2006.