↵^aTo test the scale-free property of the network, the frequency of the nodes that have degree k, denoted by f(k), was fitted to a power function of k, given by f(k) = constant·k^−λ, where λ is also the slope of the fitted line of the log-log plot for log(f(k)) regressed against log(k). Signed R² = −sgn(λ)·R². Here sgn represents the sign function; R² is the Pearson's coefficient of determination for the fitted line, whose significance is given by the p value in the last column.