要旨：Models of club good, local public good, and growth control appear to have theoretical structures distinct from usual oligopoly models. This article shows however that they are special cases of a generalized oligopoly model that incorporates the possibility of two-part pricing and externalities between consumers (either congestion or network externalities). Our generalized two-part pricing model not only serves as a synthesis of a wide range of models but also allows us to obtain several new results on equilibrium prices. Another advantage of our model is that it can be considered as a reduced form of more complicated models that have spatial structures. This allows us to easily generalize the analysis to the case where firms are heterogeneous and the number of firms is arbitrary.