Laffont, Jean-Jacques, Maskin, Eric and Rochet, Jean-Charles (1987) Optimal Nonlinear Pricing with Two-Dimensional Characteristics. In: Information, Incentives, and Economics Mechanisms: Essays in Honor of Leonid Hurwicz Groves, Theodore, Radner, Roy and Reiter, Stanley (eds.) University of Minnesota Press. Chapter 8. pp. 256-266. ISBN 978-0-8166-6866-3