B. Affandi, T. Korver, T. Paul Geurts, H. Coelingh Bennink, and W. Gadroen, “A phase II study with a single implant contraceptive containing 3-ketodesogestrel (Implanon®): efficacy and safety”, Med J Indones, vol. 8, no. 1, pp. 25–30, Jan. 1999.