1. 1) Kankyo-sho (Ministry of the Environment): Ippan Haikibutsu no Haishutsu oyobi Shori Jyokyo Tou (Heisei 11-nendo Jisseki), (Kankyo-sho Houdou Shiryo, 2002).
2. 2) Kinzoku Kogyo Jigyo-dan (Metal Mining Agency of Japan):Hibai Mugai-ka Gijutsu Kaihatsu Jigyo Soukatsu Houkokusho, (Kinzoku Kogyo Jigyo-dan, Tokyo, 2003), pp.18-23.