Cremer, Helmuth, Grimaud, André and De Rycke, Marc (1994) Alternative Scenarios for the Reform of Postal Services: Optimal Pricing and Welfare. In: Commercialization of Postal and Delivery Services: National and International Perspectives Crew, Michael A. and Kleindorfer, Paul R. (eds.) Springer. Series “Topics in Regulatory Economics and Policy”, Vol. 19. Chapter 17. pp. 247-267. ISBN 978-1-4615-2784-8