<p>11985 Heckman, James J. &amp; Robb, Richard Jr., Alternative methods for evaluating the impact of interventions&nbsp; An overview, Journal of Econometrics, Elsevier, vol. 30(1-2), pages 239-267</p><p><a href="http://www.sciencedirect.com/science/article/B6VC0-4582JY6-2T/2/dc1d6c70dda783d15830b44950bce914">http://www.sciencedirect.com/science/article/B6VC0-4582JY6-2T/2/dc1d6c70dda783d15830b44950bce914</a></p><p>21982. Heterogeneity and State Dependence, NBER Reprints 0298</p><p><a href="http://ideas.repec.org/p/nbr/nberre/0298.html">http://ideas.repec.org/p/nbr/nberre/0298.html</a></p><p>3 Sending Farmers Back to School: The Impact of Farmer Field Schools in Indonesia</p><p>http://econpapers.repec.org/article/blaragrec/v_3A26_3Ay_3A2004_3Ai_3A1_3Ap_3A45-62.htm</p>