References: Akyz, Yilmaz (2005): « WTO negotiations on industrial tariffs: what are the stakes for developing countries? » RIS Discussion Paper 98. Research and information service for developing countries, New Delhi. J. Bhagwati: « Regionalism and Multilateralism: An Overview, » in Melo and Panagariya eds. New Dimensions in Regional Integration, Cambridge University Press, Cambridge. Chang Ha-Joon (2002): Kicking Away the Ladder. Anthem Press, London. Krugman, P. (1991): `Is Bilateralism Bad? in E. Helpman and A. Razin (eds.), International Trade and Trade Policy, Cambridge, Mass.: MIT Press. Summers, L., (1991): « Regionalism and the World Trading System. » – Political impact of trade and monetary zones. Wyoming: Federal Reserve Bank of Kansas City Viner, Jacob (l950): The Customs Union Issue, Carnegie Endowment for International Peace, New York.
John Williamson: « Why Capital Account Convertibility in India Is Premature, » The Economic and Political Weekly, VOL 41 No. 19 May 13 – May 19, 2006 August 10, 2009.  An example of this policy was the famous Smoot Hawley Customs Act, which pushed U.S. tariffs to a historically high level.  A customs union (Cu) offers deeper integration than a normal EPA, since Member States also apply a common external customs duty (ECC) in an EAC to a product imported from third countries, in contrast to THE PTAs for which Member States are free to maintain their individual customs barriers for goods imported from third countries. The CET may vary from product to product, but not between union partners.  Bhagwati says in another document: « Today, the main strength of regionalism is the conversion of the United States, which had so far abstained from Article XXIV. » Bhagwati (1993) 29.  Viner (1950) introduced the concepts of « trade creation » and « trade diversion » and showed that the net effects of trade liberalization on a regional basis are not clearly positive. Viner pointed out that NTPs can lead to the creation of businesses when PTA members, as a result of the formation of the regional agreement, switch from inefficient domestic producers and import more effective producers from other EPZ members. In this case, the efficiency gains are the result of both the efficiency of production and the efficiency of consumption. On the other hand, there is a shift in trade when, because of THE NTPs, members convert their imports from low-cost production to the rest of the world and import more more expensive producers into partner countries.