Crump, Richard, Gopi Shah Goda, and Kevin J. Mumford 2011 " Fertility and the personal exception Commets." 2011 American Economic Review 101: 1616-28.
Crump, Richard, Gopi Shah Goda, and Kevin J. Mumford. 2011. "Fertility and the Personal Exemption: Comment." American Economic Review 101 (4):1616-28.