1. Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES)[ http://www.cites.org ]
2. Society of Japanese Pharmacopoeia: The Japanese Pharmacopoeia. Part II. Tokyo. 10th edition. 1981.
3. Makino I, Takebe K: Bear bile and ursodeoxycholic acid. Sogo Rinsho 1982, 31: 2385-2387.
4. Jeng WS, Cheng-Low TH: Bear bile resources – past and future. Yu-Lan Chinese Medicine College Bulletin 1992, 15: 27-30.
5. Gao XM, (Ed): Chinese Materia Medica. Xiongdan. Bejing. China Chinese Medicine Publisher; 2002:160-161.