Gelman, Andrew <br/><br/>
Why ask why? :  Forward causal inference and reverse causal questions / 
Andrew Gelman and Guido Imbens 
 - Cambridge  NBER  2013 
 - 9p 
 - NBER Working Paper ;  19614 .
<br/><br/><label>Subjects--Topical Terms: </label><br/>NBERWP 19614<br/>E10767.pdf