@article{IM_1976__34_142388,
     author = {K.A. Jr. Perko},
     title = {On {Dihedral} {Covering} {Spaces} of {Knots.}},
     journal = {Inventiones mathematicae},
     pages = {77--82},
     publisher = {mathdoc},
     volume = {34},
     year = {1976},
     zbl = {0315.55006},
     url = {http://geodesic.mathdoc.fr/item/IM_1976__34_142388/}
}