@Article{ 
  XiaXu10,
  author = { Xia, Qinglan and Xu, Shaofeng },
  title = { The Exchange Value Embedded In A Transport System },
  journal = { Applied Mathematics and Optimization },
  year = { 2010 },
  volume = { 62 },
  number = { 2 },
  pages = { 229 - 252. },
  URL = { http://cvgmt.sns.it/paper/5246/ },
  note = { cvgmt preprint}
}