Helly, Walter <br/><br/>
Urban systems models 
by Walter Helly 
 - New York  Academic Press  1975 
 - x, 185p 
 - Operations research and industrial engineering .
<br/><br/><label>ISBN: </label>0123394503 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Cities and towns-Mathematical models.
<br/><br/><label>Dewey Class. No.: </label>J72 H369