Piya-Anant, Manee, Surasak Angsuwathana, Manopchai Thamkhantho, Korakot Paytay, and Gessuda Chiravacharadej. 2007. “The Comparative Study of Different Contraceptive Methods Between Copper T 380A and Norplant 6 Siriraj Experience”. Siriraj Medical Journal 59 (6):287-89. https://he02.tci-thaijo.org/index.php/sirirajmedj/article/view/246160.