Frank-Herrmann, Petra; Baur, Siegfried; Bremme, Michael; Döring, Gerhard; Godehardt, Erhard; Sottong, Ursula:
Effectiveness and acceptability of the symptothermal method of natural family planning in Germany, in: American Journal of Obstetrics and Gynecology (1991), Vol. 165, No. 6, p. 2052-2054.

Frank-Herrmann, Petra; Freundl, Günter; Gnoth, Christian; Godehardt, Erhard; Kunert, Josef; Baur, Siegfried; Sottong, Ursula:
Natural family planning with and without barrier method use in the fertile phase: efficacy in relation to sexual behaviour: a German prospective long-term study, in: Advances in Contraception (1997), Vol. 13, No. 2-3, p. 179-189.

Frank-Herrmann, Petra; Gnoth, Christian; Sottong, Ursula et al.:
Effectiveness of various approaches to NFP & beyond scientific choice of NFP methodology, R.J. Fehring, Theresa Notare (Eds.), Marquette University Press, Milwaukee 1008, in: Human Fertility (2008), p. 142-155.

Frank-Herrmann, Petra; Heil, J.; Gnoth, Christian et al.:
The effectiveness of a fertility awareness based method to avoid pregnancy in relation to a couple’s sexual behaviour during the fertile time: A prospective longitudinal study, in: Human Reproduction (2007), Vol. 22, Nr. 5, p. 1310-1319.

Freundl, Günter; Baur, Siegfried; Bremme, Michael; Frank-Herrmann, Petra; Sottong, Ursula:
Preliminary results of the prospective european NFP-efficiency study 1992 (Ongoing). III. Symposium internacional sobre avances en regulación natural de la fertilidad, Malaga 1994, in: Kongressbericht Malaga, S. 135-144.

Freundl, Günter:
Prospective european multicenter study of the effectiveness and acceptability of natural family planning (1989-1994). VIth. World Congress, International Federation for Family Life Promotion, September 16-24, 1994, Lublin/Poland, in: Proceedings Lublin, p. I-1.

Freundl, Günter; Frank-Herrmann, Petra; Brown, Simon; Blackwell, Leonard:
A new method to detect significant basal body temperature changes during a woman’s menstrual cycle, The European Journal of Contraception and Reproductive Health Care, 2014; 19: 392-400