@article{MS2_1972__30_166227,
     author = {Frank Wattenberg},
     title = {Differentiable {Motions} of {Unknotted,} {Unlinked} {Circles} in {3-Space.}},
     journal = {Mathematica Scandinavica},
     pages = {107--135},
     publisher = {mathdoc},
     volume = {30},
     year = {1972},
     zbl = {0248.55003},
     url = {http://geodesic.mathdoc.fr/item/MS2_1972__30_166227/}
}