Metric Spaces of Non-Positive Curvature - Martin R. Bridson, André Häfliger - Google Books

http://books.google.de/books/about/Metric_Spaces_of_Non_Positive_Curvature.html?id=3DjaqB08AwAC&redir_esc=y

The purpose of this book is to describe the global properties of complete simply connected spaces that are non-positively curved in the sense of A. D. Alexandrov and to examine the structure of groups that act properly on such spaces by isometries. Thus…