sentences:  "head") node of edge formula_18.We indicate average values with bars, so that formula_24, and formula_25 are the average formula_20-degree of sources, and formula_22-degree of targets, respectively; averages being taken over the edges of the network.Finally, we have
  
  formula_28
  
  Another means of capturing the degree correlation is by examining the properties of formula_29, or the average degree of neighbors of a node with degree "k".