1. Experience with LNG for postcoital contraception;Canzler;Zentralblatt für Gynäkologie,1984
2. Prospective study of contraception with LNG;Chernev;Planned Parenthood in Europe,1995
3. The pre-coital use of mini-dosage progestagens;Cox;Journal Reproduction and Fertility,1968
4. Echeverry G Sarria C High doses of d-norgestrel as a postcoital contraception Report on file 1974
5. A multicenter clinical study on two types of LNG tablets administered for postcoital contraception;He;International Journal of Gynecology and Obstetrics,1991