Cremer, Helmuth, De Donder, Philippe, Dudley, Paul and Rodriguez, Frank (2006) Pricing and Welfare Implications of Alternative Approaches to Setting Price Controls in the Postal Sector. In: Progress Toward Liberalization of the Postal and Delivery Sector Springer. Series “Topics in Regulatory Economics and Policy” pp. 227-248. ISBN 978-0-387-29743-9