Luvoni, G. C., & Grioni, A. (2000).Determination of gestational age in medium and small size bitches using ultrasonography measurement of foetal structures.
Beccaglia, M., & Luvoni, G. C. (2006).Ultrasonographic fetal biometry in dogs and cats.Reproduction in Domestic Animals, 41(2), 136–140.
Yeager, A. E., Mohammed, H. O., Meyers-Wallen, V. N., Vannerson, L., & Concannon, P. W. (1992).Ultrasonographic appearance of the uterus, placenta, fetus, and fetal membranes throughout accurately timed pregnancy in Beagles.American Journal of Veterinary Research, 53(3), 342–351.