Freedman, Paul. <br/><br/>
The principles of scintific research 

 - 2 ed. 
 - Oxford :  Pergamon Press,  1960 
 - 228 p. 
<br/><br/><label>LCCN: </label>43107 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Investigación.
<br/><br/><label>Dewey Class. No.: </label>507.2  / F74