Unobtrusive measures /  
Eugene J. Webb ... [et al.]. 
 - rev. ed. 
 - Thousand Oaks, Calif. :  Sage Publications,   2000. 
 - xix, 220 p. ;  24 cm. 
 - Sage classics series ;  2 .
<br/><br/> Rev. ed. of: Nonreactive measures in the social sciences. 2nd ed. 1981. 
<br/><br/>Includes bibliographical references (p. 189-209) and index. 
<br/><br/><label>ISBN: </label>0761920129 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Social sciences--Research
<br/><br/><label>Dewey Class. No.: </label>300.72