4Keeler J P, Formby J P. Cost Economies and Consohdation in the US Airline Industry [ J ] . International Journal of Transport Economics.1994, 21(1): 21-45.
5Oum T H. Zhang Y. A Note on Scale Economies in Transport[J]. Journal of Transport Economies and Policy, 1997(9) : 309 -315.
7Keaton M H. Economies of Density and Service Levels on US Railroad: An Experimental Analysis[J]. Logistics and Transportation Review, 1990, 26 (3): 211- 227.
8FANG Xiao-ping, Scale and scope economies based on net characteristic of railway transportation and its application[J]. International Conference on Transportation Engineering, 2007, ICTE 2007,154 - 159.
9Jara D S R, Cortes C E. On the calculation of scale economies from transport cost functions [ J ]. Journal of Transport Economics and Policy, 1996, (30), 157- 170.
10Yang X, Borland J. A microeconomic mechanism for economic growth[ J ]. Journal of Political Economy. 1991, ( 99 ) : 460 - 482.