求3篇早期英文文献,写作急用,谢谢!

(1)Caplin,Andrew and kala,Krishna(1998).Tariffs and the most-favored-nation clause:Agame-theoretic approach. Seoul Journal of Economics 1:267-289

(2)Ludema,Rodney(1991).International trade bargaining and the most-favored-nation clause.Economics and Politics 3:1-20

(3)Johnson,Harry(1965)..An Economic Theory of Protectionism, Tariff Bargaining, and the Formation of Customs Unions.Journal of Political Economy. 256-283