Helmuth Cremer, André Grimaud, and Marc de Rycke, “Costs and Benefits of Universal Service Obligations in the Postal Sector”, in Managing Change in the Postal and Delivery Industries, Michael A. Crew, and Paul R. Kleindorfer (eds.), Kluwer, series “Topics in Regulatory Economics and Policy”, vol. 25, chapter 2, 1997, pp. 22–41.