2LIN Cheng-chang, LIN Yu-jen,LIN Dung-ying. The eco-nomic effects of center-to-center directs on hub-and-spokenetworks for air express common carriers[ J]. Journal of AirTransport Management, 2003 (9) : 255 -265.
3GRUNERTT, SEBASTIAN H J. Planning models for long-haul operations of postal and express shipment companies[J ]. European Journal of Operational Research,2000,122: 289 -390.