Geer, Helen Thornton. <br/><br/>
Charging systems / 
Helen Thornton Geer. 
 - Chicago :   ALA,   1955. 
 - xii, 177 p. ;  ill. ;  23 cm. 
<br/><br/>Includes Bibliography  
<br/><br/>400  400 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Charging systems (Libraries).
<br/><br/><label>Dewey Class. No.: </label>020 / G271c