APA-referens (7:e uppl.)

Heckman, J. L. (1999). Causal parameters and policy analysis in economics: A twentieth century retrospective. National Bureau of Economic Research.

Chicago-referens (17:e uppl.)

Heckman, James L. Causal Parameters and Policy Analysis in Economics: A Twentieth Century Retrospective. Cambridge: National Bureau of Economic Research, 1999.

MLA-referens (9:e uppl.)

Heckman, James L. Causal Parameters and Policy Analysis in Economics: A Twentieth Century Retrospective. National Bureau of Economic Research, 1999.