Struve, Otto. <br/><br/>
Astronomy of the 20th century   
by Otto Struve, Valta Zebergs. 
 - New york  Macmillan Company  1962 
 - 544p. 
<br/><br/><label>LCCN: </label>62-21206 
<br/><br/><label>Dewey Class. No.: </label>520  / N621