I. Moerdijk, CLASSIFYING-SPACES, CLASSIFYING TOPOI AND AUGMENTED ORDERS, Comptes rendus de l'Academie des sciences. Serie 1, Mathematique, 317(3), 1993, pp. 293-298
It is shown that the classifying space of a topological category has t
he same weak homotopy type as the classifying topos. As a consequence,
mappings from a CW-complex X into the classifying topos. As a consequ
ence, mappings from a CW-complex X into the classifying space are show
n lo correspond to concordance classes of augmented orders over X.