@article{CTGDC_1979__20_1_3_0,
     author = {Porter, Timothy},
     title = {Essential properties of pro-objects in {Grothendieck} categories},
     journal = {Cahiers de topologie et g\'eom\'etrie diff\'erentielle},
     pages = {3--57},
     publisher = {Dunod \'editeur, publi\'e avec le concours du CNRS},
     volume = {20},
     number = {1},
     year = {1979},
     mrnumber = {544528},
     zbl = {0414.18006},
     language = {en},
     url = {http://archive.numdam.org/item/CTGDC_1979__20_1_3_0/}
}