The late Dr. James Brown worked since 1947 on the application of hormone assays in the identification of the phases of fertility and infertility during the menstrual cycle in Auckland, New Zealand; in Edinburgh, Scotland (1949-1962) and in Melbourne, Australia (1962-2009).
In Edinburgh he was involved in the development of the first accurate hormone assays for estrogens, pregnanediol and total gonadotrophins in urine, and later, in Melbourne, refined the assays for estrogens and pregnanediol for rapid and mass application. During the 1960s, Dr. Brown used these assays in helping Drs. John and Lyn Billings develop and validate the Ovulation Method.
Dr. Brown performed 750,000 hormonal correlations that confirmed that the simple observations of the signs that the woman observes during the fertile phase coincide with the hormonal correlations performed in the laboratory.
Further extensive information can be found in the book "Love and Fertility".