Ruffin, Roy J. <br/><br/>
Principles of economics/ 
Roy J. Ruffin and Paul R. Gregory 
 - 4th ed. 
 - Illionois:   Scott, Foreman/Little, Brown Higher Education, a division of Scott, Foreman and Company,   1990. 
 - xxxii, 851p.:   ill. 
<br/><br/>Includes bibliographical references and index 
<br/><br/><label>ISBN: </label>0673460207 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Economics
<br/><br/><label>LC Class. No.: </label>HB 171.5 RUF 1990