5Grubel, H.G. , and LIoyd, P. J. Intra - industry Trade: The Theory and Measurement of International Trade in Differentiated Products [ J ]. London : Macmillan, 1975.
6Balassa, B. Trade Liberalization and Revealed Comparative Advantage [ J ]. The Manchester School of Economics and Social Studies 33, 1965, pp. 99 - 123.