Wallen. N.E. <br/><br/>
Educational research:  a guide to the process/ 
Norman E.Wallen ; Jack R. Fraenkel. 
 - London:  Lawrence Erlbaum associates,  2001. 
 - xix,548p.:  ill,:  24 cm 
<br/><br/> Includes bibliography references and index 
<br/><br/><label>ISBN: </label>9780805832808 
<br/><br/><label>LC Class. No.: </label>DUCE LB1028.W275