A Firm Specific Analysis of Economies of Density in the U.S. Railroad Industry
针对美国铁路行业，从公司层面分析密度经济的存在性及其特征，为理解铁路运营效率提供实证依据。
Ronald R. Braeutigam, Andrew F. Daughety, Mark A. Turnquist, A Firm Specific Analysis of Economies of Density in the U.S. Railroad Industry, The Journal of Industrial Economics, Vol. 33, No. 1 (Sep., 1984), pp. 3-20