From the reviews: “To provide an operational definition early on, to help guide the reader … . book is a quick read, and is generally accessible to scholars and students with an intermediate background in econometrics or applied statistics. … greatest interest to regional scientists, economists, and economic geographers who are already familiar with contemporary research on knowledge spillovers and network externalities and want to keep up with new empirical results.” (Henry Renski, Journal of Regional Science, Vol. 50 (2), 2010)