1. Pregnancy Diagnosis in the Sow by Rectal Examination;Cameron;Austral. Vet. J.,1977
2. Pregnancy Diagnosis in the Sow by Examination of the Uterine Arteries;Meredith,1976
3. Early Diagnosis of Pregnancy in Sows by Ultrasonic Amplitude-Depth Analysis;Lindahl;J. of Anim. Sci.,1975
4. Pregnancy Diagnosis in Pigs by Ultrasonic Amplitude — Depth Analysis — A Field Evaluation;O'Reilly;Irish Vet. J.,1976
5. A New Method of Early Detection of Pregnancy in the Sow;Berthelsen;Iowa State University, Vet.,1973