TY  - RPRT
TI  - Ovulation method of contraception.
AU  - J J Billings
PY  - 1981
DO  - 10.5694/j.1326-5377.1981.tb135299.x
UR  - https://pubmed.ncbi.nlm.nih.gov/7207299/
ID  - 7207299
ER  -