Blalock, Hubert M. <br/><br/>
Causal inferences in nonexperimental research / 
by Hubert M. Blalock, Jr 
 - Norton :  New York,  1972 
 - xii, 200 p. :  ill. ;  20 cm. 
<br/><br/>Bibliography : p. 193 
<br/><br/><label>ISBN: </label>0393006425 
<br/><br/><label>LCCN: </label>72-002903 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Social sciences--Mathematical models