The Relative Valuation of Caps and Swaptions: Theory and Empirical Evidence
Francis Longstaff, Pedro Santa Clara, Eduardo Schwartz
Journal of Finance, vol. 56, 2001, p. 2067-2109.

Throwing Away a Billion Dollars: The Cost of Suboptimal Exercise Strategies in the Swaptions Market
Francis Longstaff, Pedro Santa Clara, Eduardo Schwartz
Journal of Financial Economics, vol. 62, 2001, p. 39-66.