Helly, Walter <br/><br/>
Urban systems model / 
Walter Helly 
 - x, 185 pages :  illustrations ;  21 cm 
<br/><br/> Includes index 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Cities and towns --Mathematical models
<br/><br/><label>Dewey Class. No.: </label>301.364