@article{CTGDC_1985__26_4_381_0,
     author = {Porter, Timothy},
     title = {Crossed modules in $Cat$ and a {Brown-Spencer} theorem for $2$-categories},
     journal = {Cahiers de Topologie et G\'eom\'etrie Diff\'erentielle Cat\'egoriques},
     pages = {381--388},
     publisher = {Dunod \'editeur, publi\'e avec le concours du CNRS},
     volume = {26},
     number = {4},
     year = {1985},
     mrnumber = {816647},
     zbl = {0575.18006},
     language = {en},
     url = {http://archive.numdam.org/item/CTGDC_1985__26_4_381_0/}
}