Her The Billings method, 1981, c1980: t.p. (Dr. Evelyn Billings) CIP publisher info. (Evelyn L. Billings; specialist pediatrician; lives in Melbourne, Australia)
LC/NAF 12 January 2018 (Billings, Evelyn)
The Billings enigma, 2013: p. 1 (born February 8, 1918) p. 153 (died Feb. 2013)
Wikipedia 12 January 2018 (Dr. John Billings, AM, KC*SG, FRCP, FRACP (5 March 1918-1 April 2007) and his wife Evelyn Livingston Billings (née Thomas) AM, DC*SG (8 February 1918-16 February 2013) were Australian physicians who pioneered the natural method of family planning known initially as the Ovulation Method, then the Ovulation Method Billings, specified by the WHO in 1978 and finally as the Billings Ovulation Method.) https://en.wikipedia.org/wiki/John_and_Evelyn_Billings