Bo E. Honoré and James L. Powell, Pairwise difference estimators of censored and truncated regression models, Journal of Econometrics, Volume 64, Issues 1-2, September-October 1994, Pages 241-278. (http://www.sciencedirect.com/science/article/B6VC0-459B9P0-F/1/84dc5edf704575d12bda0abfb233a3a0)