HECKMAN James J <br/><br/>
Simple statistical and applied to test  the hypothesis of true state dependence against the hypothesis of spurious state dependence . 
HECKMAN James J 
 - Chicago  University of Chicago          1977 
 - 39p.  cm. 
<br/><br/><label>Source: </label> General Book 
<br/><br/><label>Dewey Class. No.: </label>X:B(28).N77r, L1