Siegmund, O., Fraser, C., Archibald, J., Blood, D., Henderson, J., Howell, D., . . . Soffer, L. (1973). The Merck veterinary manual (4. ed.). New Jersey (EUA): Merck Co..

Siegmund, O.H., C.M Fraser, J. Archibald, D.C Blood, J.A Henderson, D.G Howell, R.L Kitchell, and L. Soffer. The Merck Veterinary Manual. 4. ed. New Jersey (EUA): Merck Co., 1973.

Siegmund, O.H., et al. The Merck Veterinary Manual. 4. ed. New Jersey (EUA): Merck Co., 1973.