@article{MAN_1981__257_163548,
     author = {C.McA. Gordon},
     title = {Ribbon {Concordance} of {Knots} in the {3-Sphere.}},
     journal = {Mathematische Annalen},
     pages = {157--170},
     year = {1981},
     volume = {257},
     zbl = {0451.57001},
     url = {http://geodesic.mathdoc.fr/item/MAN_1981__257_163548/}
}