English: A world map of countries per the four-network block model, 1965, using the world system differentiation into blocks A, B, C, C', D, D', E, E', F and F'. by David Snyder and Edward Kick: "Structural Position in the World Systems and Economic Growth, 1955-1970: A Multiple-Network Analysis of Transnational Interactions" in The American Journal of Sociology, Vol. 84, No. 5 (Mar., 1979), pp. 1096-1126.
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