![The Billings Ovulation Method®](https://d2j6dbq0eux0bg.cloudfront.net/images/4761406/619731652.jpg)
A teaching resource which explains the variations in cycle length and the application of the Rules of the Billings Ovulation Method®. A necessary resource for all Billings Ovulation Method® teachers and other health professionals to assist women and couples to understand the phases of the ovarian cycle.