TY  - RPRT
TI  - Sharp increase in free circulating oestrogens immediately before parturition in sheep.
AU  - J R Challis
PY  - 1971
DO  - 10.1038/229208a0
UR  - https://pubmed.ncbi.nlm.nih.gov/4923273/
ID  - 4923273
ER  -