Wilkinson, T.C., "Cloth and Currency: On the Ritual-Economics of Eurasian Textile Circulation and the ‘Origins’ of Trade, Fifth to Second millennia BC" a Kristiansen, K.; Lindkvist, T.; Myrdal, J., Trade and Civilization: Economic Networks and Cultural Ties, from Prehistory to the Modern Era, Cambridge University Press, Cambridge, p. 25-55.