Bridson, Martin R. and Haefliger, Andre <br/><br/>
Metric spaces of non-positive curvature   

 - Berlin  Springer-Verlag  1999 
 - xxi, 643p. Bibl. Index. 
 - Grundlehren der Mathematischen Wissenschaften    319 .
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<br/><br/><label>ISBN: </label>3540643249 
<br/><br/><label>Dewey Class. No.: </label>516  / B852.MS