Cita APA (7a ed.)

Mulligan, C. B., & Sala i Martín, X. (1999). Social security in theory and practice. National Bureau of Economic Research.

Cita Chicago Style (17a ed.)

Mulligan, Casey B., y Xavier Sala i Martín. Social Security in Theory and Practice. Cambridge, MA: National Bureau of Economic Research, 1999.

Cita MLA (9a ed.)

Mulligan, Casey B., y Xavier Sala i Martín. Social Security in Theory and Practice. National Bureau of Economic Research, 1999.