Walter Helly <br/><br/>
Urban systems models 

 - London<br/>  Academic press  1975 
 - 185, ill 
<br/><br/><label>ISBN: </label>0 12 339450 3 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Urbanization
<br/><br/><label>Dewey Class. No.: </label>307.12  / HEL