Eberlein, Patrick <br/><br/>
Surfaces of nonpositive curvature   
by Patrick Eberlein 
 - Providence  American Mathematical Society  1979 
 - x, 90p. 
 - Memoirs of the American Mathematical Society 218 .
<br/><br/><label>ISBN: </label>0821822187 
<br/><br/><label>Dewey Class. No.: </label>516.362  / N79