Atlas of the ovulation method :
Billings, Evelyn.
Atlas of the ovulation method : the mucus patterns of fertility and infertility / Evelyn L. Billings, John J. Billings and Rev. Maurice Catarinich. - 3rd ed. - Melbourne, Australia : Advocate P, 1979.
Ovulation.
Atlas of the ovulation method : the mucus patterns of fertility and infertility / Evelyn L. Billings, John J. Billings and Rev. Maurice Catarinich. - 3rd ed. - Melbourne, Australia : Advocate P, 1979.
Ovulation.