Bergmann, Peter Gabriel. <br/><br/>
The riddle of gravitation / 
Peter G. Bergmann. 
 - New York :  Scribner,  [1968] 
 - xvi, 270 p. :  ill., ports. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Relativity (Physics)<br/>Gravitation.