臺美牛肉議定書 牛海綿狀腦病 一九六九年維也納條約法公約 世界貿易組織 Protocol of bovine spongiform encephalopathy (BSE)-related measures for the importation of beef and beef products for human consumption from the territory of the authorities represented by the American institute in Taiwan(AIT) Bovine spongiform encephalopathy BSE 1969 Vienna convention on the law of treaties World Trade Organization WTO