Does there exist a survey on the early developments of CAT(k) spaces, with the first motivations and the first problems considered? I looked at Bridson and Haefliger's book On metric spaces of non-positive curvature, and I only found the following references:
Rinow, Die innere Geometrie der metrischen Raüme. On the period to 1960. However, the book is written in German.
Two papers of Alexandrov, written in Russian.
Gromov, Hyperbolic groups. Where the term CAT(k) is coined. However, I did not see historical considerations nor references.
The first point is that I do not read German nor Russian... Anyway, these references are old and necessarily are far from being exhaustive nowadays. Do you know if there exists a good reference on the subject?