Helly Walter <br/><br/>
Urban system models 
Helly Walter 
 - New York  Academic Press USA         1975 
 - x, 185p. Bibliography chapterwise  cm. 
<br/><br/> Operations research and industrial engineering 
<br/><br/><label>Source: </label> General Book 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Regional Economics
<br/><br/><label>Dewey Class. No.: </label>X:89K33: (B), L5