1. Variations in bull semen and their relation to fertility;Swanson E.;J. Dairy Sci.,1941
2. Observations upon the seminal micropathology of bulls;Williams W.;Cornell Vet.,1925
3. Sterility in bulls;Lagerlof N.;Vet. Rec.,1936
4. Manual for the breeding soundness examination of bulls;Ball L.;Theriogenology,1983