Mostly harmless econometrics : an empiricist's companion / Joshua D. Angrist, Jorn-Steffen Pischke Angrist, Joshua D. Pischke, Jorn-Steffen Au. Econometrics 22 330.015195 ANM Includes bibliographical references and index New Jersey : Princeton University Press, 2009 2009 2009 Text xvii, 373 P. : eng