APA
Heckman J. J., Smith J. A., . (1999). The pre-program earnings DIP and the determinants of participation in a social program : implications for simple program evaluation strategies. Cambridge, Mass: National Bureau of Economic Research.
Chicago
Heckman James J, Smith Jeffrey A, . 1999. The pre-program earnings DIP and the determinants of participation in a social program : implications for simple program evaluation strategies. Cambridge, Mass: National Bureau of Economic Research.
Harvard
Heckman J. J., Smith J. A., . (1999). The pre-program earnings DIP and the determinants of participation in a social program : implications for simple program evaluation strategies. Cambridge, Mass: National Bureau of Economic Research.
MLA
Heckman James J, Smith Jeffrey A, . The pre-program earnings DIP and the determinants of participation in a social program : implications for simple program evaluation strategies. Cambridge, Mass: National Bureau of Economic Research. 1999.