1. Contraceptive methods requiring medical assistance;Lehfeldt, H.
2. The intrauterine method of contraception;Grafenberg, E.
3. An intrauterine contraceptive method;Grafenberg, E.
4. A study of intrauterine contraception: development of a plastic loop;Lippes, J.,1963
5. Clinical experience with the use of a flexible nylon ring (Grafenberg ring) as a contraceptive technique;s Zipper JA; HD, Sanhueza,1963