2RAMANA K V,RAO A S,NAIDU K V,et al.Studies on estrus cycle in cross-bred pigs [J].Indian Journal of Animal Reproduction, 2000,21 (2) : 128-130.
3Ramana K V, Pao A S, Naidu K V. et al. Studies on estrus cycle in cross - bred pigs[J]. Indian Journal of Animal Reproduction,2000, 21 (2) : 130 - 138.