@article{10_4153_CJM_1981_068_6,
     author = {Vermeer, Hans and Wattel, Evert},
     title = {Projective {Elements} in {Categories} with {Perfect} {\ensuremath{\theta}-Continuous} {Maps}},
     journal = {Canadian journal of mathematics},
     pages = {872--884},
     year = {1981},
     volume = {33},
     number = {4},
     doi = {10.4153/CJM-1981-068-6},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1981-068-6/}
}