On locally simply connected toposes and their fundamental groups
Cahiers de Topologie et Géométrie Différentielle Catégoriques, Volume 22 (1981) no. 3, p. 301-314
@article{CTGDC_1981__22_3_301_0,
     author = {Barr, Michael and Diaconescu, Radu},
     title = {On locally simply connected toposes and their fundamental groups},
     journal = {Cahiers de Topologie et G\'eom\'etrie Diff\'erentielle Cat\'egoriques},
     publisher = {Dunod \'editeur, publi\'e avec le concours du CNRS},
     volume = {22},
     number = {3},
     year = {1981},
     pages = {301-314},
     zbl = {0472.18002},
     mrnumber = {649078},
     language = {en},
     url = {http://www.numdam.org/item/CTGDC_1981__22_3_301_0}
}
On locally simply connected toposes and their fundamental groups. Cahiers de Topologie et Géométrie Différentielle Catégoriques, Volume 22 (1981) no. 3, pp. 301-314. http://www.numdam.org/item/CTGDC_1981__22_3_301_0/

M. Barr, Exact categories, Lecture Notes in Math. 236, Springer (1971). | Zbl 0223.18010

M. Barr, Building closed categories, Cahiers Topo. et Géom. Diff. XIX- 2 (1978), 115-130. | Numdam | MR 528341 | Zbl 0381.18016

M. Barr & R. Diaconescu, Atomic toposes, J. Pure Appl. Algebra 17 (1980) 1-24. | MR 560782 | Zbl 0429.18006

M.B. Arr & R. Pare, Molecular toposes, J. Pure Appl. Algebra 17 (1980), 127-152. | MR 567064 | Zbl 0436.18002

C. Chevalley, Theory of Lie groups, Princeton University Press, 1946. | Zbl 0063.00842

Sgal (dirigé par A. Grothendieck), Revêtements étales et groupe fondamental, Lecture Notes in Math. 224, Springer (1971). | MR 354651