Early Childhood Development on a Large Scale, Grunewald, Rob and Rolnick, Art
http://www.minneapolisfed.org/publications_papers/pub_display.cfm?id=3279
Heckman: The Economics of Human Potential
http://heckmanequation.org
Think Progress: Five Surprising Facts About Early Childhood Education
http://thinkprogress.org/education/2013/06/05/2104771/five-surprising-facts-about-early-childhood-education/
The Ounce of Prevention: Why Investments in Early Childhood Work
http://www.ounceofprevention.org/about/why-early-childhood-investments-work.php
Early Childhood Education for All: A Wise Investment
http://web.mit.edu/workplacecenter/docs/Full%20Report.pdf