title: Efficacy of natural family planning methods.
authors.forename: Günter
authors.initials: G
authors.lastname: Freundl
mesh_terms: D003276:Contraceptives, Oral; D005260:Female; D006801:Humans; D012252:Natural Family Planning Methods; D049168:Pregnancy, Unplanned
chemical_list: D003276:Contraceptives, Oral