TITLE: History of the notion of $(G,X)$-structure
QUESTION [13 upvotes]: I'm currently searching for sources and historical basis on the notion of $(G,X)$-structure as it appears in Thurston's work.
So far, it appears that he was the first to set it. Many mathematicans cite Ehresmann's work, also I'm not sure to what precisely. It also seems that Kuiper (On compact conformally Euclidean spaces of dimension $> 2$, 1950) also had some ideas close to what we call a developing map, and related to the idea to put a structure on a manifold.
Maybe someone here already have made such researches, or could testify ?
Thanks
edit : 
As requested, I specify a sense of $(G,X)$-structure. I mean by that a pair of $G$ a group (or pseudo-group if wanted) of analytic diffeomorphisms of $X$, a smooth analytic connected manifold.
The point is to have $(G,X)$-structure notion clean enough to get the pair of a developing and holonomy maps.

REPLY [3 votes]: how do i guess n. kuiper learned about the developing mapping of a G structure.? 
kuiper and everyone before the war learned and used projective geometry. also in holland brouwers tradition was felt and he and other differential geometers thought geometrically in terms of developable surfaces, and the developing idea of curvature. I think ehreshmann was formalizing this intuition. kuipers papers 49-50 were also formalizing this in a more geometric way....ereshmanns lectures were very formal and abstract ( reported by tony phillips who attended them in early 60's as a fulbright scholar in france.)  covering spaces and these ideas are taught everywhere but they are non trivial. one sees that in the work of thurstion who found important new phenomena of holonomy of developments in very classical examples like gluing two ideal noneuclidean triangle together.  dennis sullivan