Natural Oligopolies: A Vertical Differentiation Model
更完整地刻画了垂直差异化市场成为或不成为自然寡头的条件，扩展了之前关于成本函数为常数规模报酬的结论，并提供了边际成本递增或递减情形下的结果。
This article contains a more complete characterization of conditions under which vertically differentiated markets are or are not natural oligopolies than has been found previously in the literature. Specifically, previous results on markets in which firms have cost functions with constant returns are incomplete; these results are expanded. Moreover, results are provided for markets with firms having increasing or decreasing marginal cost functions.