Campbell, Donald T,  -. <br/><br/>
Experimental and quasi-experimental designs for research :  - / 

 - 
 - Chiacago :  Rand McNally & Co,  1969. 
 - p. 84:ill :  - ;   cm.15. 
 - .
<br/><br/> -. 
<br/><br/>Includes index and bib refs. 
<br/><br/> -. 
<br/><br/><label>ISBN: </label> - 
<br/><br/><label>Subjects--Topical Terms: </label><br/>research---.<br/>----.<br/>----.