@article{10_4153_CJM_1992_007_4,
     author = {Hempel, John},
     title = {Homology of {Branched} {Coverings} of {3-Manifolds}},
     journal = {Canadian journal of mathematics},
     pages = {119--134},
     year = {1991},
     volume = {44},
     number = {1},
     doi = {10.4153/CJM-1992-007-4},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1992-007-4/}
}