Article in a refereed journal:

Jean-Charles Rochet and Jean Tirole, "Tying in Two-Sided Markets and the Honor All Cards Rule", International Journal of Industrial Organization, vol. 26, n. 6, November 2008, p. 1333-1347. doi:10.1016/j.ijindorg.2008.01.002.

Jean-Charles Rochet and Jean Tirole, "Tying in Two-Sided Markets and the Honor All Cards Rule", IDEI Working Paper, n. 440, February 2006, revised 2007.