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@article{IM_1982__67_142904, author = {John Hempel}, title = {Orientation {Reversing} {Involutions} and the {First} {Betti} {Number} for {Finite} {Coverings} of {3-Manifolds.}}, journal = {Inventiones mathematicae}, pages = {133--142}, publisher = {mathdoc}, volume = {67}, year = {1982}, zbl = {0494.57003}, url = {http://geodesic.mathdoc.fr/item/IM_1982__67_142904/} }
John Hempel. Orientation Reversing Involutions and the First Betti Number for Finite Coverings of 3-Manifolds.. Inventiones mathematicae, Tome 67 (1982), pp. 133-142. http://geodesic.mathdoc.fr/item/IM_1982__67_142904/