Campbell, Robert Norman <br/><br/>
Photoelectric cells 
Norman Robert Campbell and Dorothy Ritchie. 
 - London  Sir Isaac Pitman and Sons  1929 
 - vii, 209p. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Astronomy and Astrophysics Thesaurus
<br/><br/><label>Universal Decimal Class. No.: </label>621.383  / CAM