between tiers of nodes but also the prices of the product at the various tiers. The model
therein was, subsequently, generalized to include electronic commerce by Nagurney, Loo,
Dong, and Zhang (2002). Nagurney (2006a) proved that supply chain network equilibrium
problems could be transformed and solved as transportation network equilibrium problems
and novel interpretations of the underlying equilibrium conditions given in terms of paths and
path flows. More recently, Nagurney and Liu (2005) and Wu, Nagurney, Liu, and Stranlund
(2006) proved, as hypothesized in Beckmann, McGuire, and Winsten (1956), that electric
power generation and distribution networks could also be tranformed into transportation
network equilibrium problems, thus resolving a hypothesis that was open for over 50 years.
Finally, Liu and Nagurney (2006) established that financial networks with intermediation
could also be transformed into transportation networks over appropriately constructed abstract
networks or supernetworks. Zhang, Dong, and Nagurney (2003), in turn, generalized
Wardrop’s principle(s) to consider not only routes but chains in the network to identify the
“winning” supply chains. In that context, routes correspond to production processes and
links can be either operation or interface links. Their framework allows for the modeling of
competition between supply chains, which may entail several firms (producing, transporting,
retailing, etc.).