Flowers, Thomas Harold. <br/><br/>
Introduction to exchange systems / 
T. H. Flowers. 
 - London :  Wiley,  1976. 
 - xvii, 326 p. :  ill. 
<br/><br/> "A Wiley interscience publication" 
<br/><br/><label>ISBN: </label>047018651 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Telephone stations.