APA

Frank-Herrmann P., Freundl G., Gnoth C., Godehardt E., Kunert J., Baur S. & Sottong U. (19971015). Natural family planning with and without barrier method use in the fertile phase: efficacy in relation to sexual behavior: a German prospective long-term study. : Advances in contraception : the official journal of the Society for the Advancement of Contraception.

Chicago

Frank-Herrmann P, Freundl G, Gnoth C, Godehardt E, Kunert J, Baur S and Sottong U. 19971015. Natural family planning with and without barrier method use in the fertile phase: efficacy in relation to sexual behavior: a German prospective long-term study. : Advances in contraception : the official journal of the Society for the Advancement of Contraception.

Harvard

Frank-Herrmann P., Freundl G., Gnoth C., Godehardt E., Kunert J., Baur S. and Sottong U. (19971015). Natural family planning with and without barrier method use in the fertile phase: efficacy in relation to sexual behavior: a German prospective long-term study. : Advances in contraception : the official journal of the Society for the Advancement of Contraception.

MLA

Frank-Herrmann P, Freundl G, Gnoth C, Godehardt E, Kunert J, Baur S and Sottong U. Natural family planning with and without barrier method use in the fertile phase: efficacy in relation to sexual behavior: a German prospective long-term study. : Advances in contraception : the official journal of the Society for the Advancement of Contraception. 19971015.