Cita APA (7a ed.)

Levitt, S. D., & Porter, J. R. (1999). Sample selection in the estimation of air bags and seat belt effectiveness. National Bureau of Economic Research.

Cita Chicago Style (17a ed.)

Levitt, Steven D., y Jack Ray Porter. Sample Selection in the Estimation of Air Bags and Seat Belt Effectiveness. Cambridge, MA: National Bureau of Economic Research, 1999.

Cita MLA (9a ed.)

Levitt, Steven D., y Jack Ray Porter. Sample Selection in the Estimation of Air Bags and Seat Belt Effectiveness. National Bureau of Economic Research, 1999.