Cita APA (7a ed.)

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. National Bureau of Economic Research.

Cita Chicago Style (17a ed.)

Heckman, James J., y Jeffrey A. Smith. The Pre-Program Earnings Dip and the Determinants of Participation in a Social Program: Implications for Simple Program Evaluation Strategies. Cambridge, Massachusetts: National Bureau of Economic Research, 1999.

Cita MLA (9a ed.)

Heckman, James J., y Jeffrey A. Smith. The Pre-Program Earnings Dip and the Determinants of Participation in a Social Program: Implications for Simple Program Evaluation Strategies. National Bureau of Economic Research, 1999.