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Treatment Effect Bounds: An Application to Swan-Ganz Catheterization; Jay Bhattacharya, Azeem Shaikh and Edward Vytlacil; NBER Working Papers Series no. 11263; Cambridge: National Bureau of Economic Research 2005. Threshold Crossing Models and Bounds on Treatment Effects: A Nonparametric Analysis; Azeem Shaikh and Edward Vytlacil; NBER Technical Working Papers no. 0307; Cambridge: National Bureau of Economic Research, 2005.