“…Purchasing and sales linkages provide one means for transmitting both codified and tacit knowledge between firms, in terms of technology, skills, products or new management ideas (Midmore et al, 2006). Thus, tighter buyer--supplier linkages may provide agglomeration externalities (Steen and Hansen, 2013;Boschma & Frenken, 2011) within clusters. Considering the complexity of these inter--linked elements, it would be an enormous task to trace and measure the backward and forward links between each of the firms, as well as their external connections within a cluster (Cai and Lueng, 2002).…”