@article{GT_2014_18_5_a9,
     author = {Grove, Karsten and Wilking, Burkhard},
     title = {A knot characterization and 1{\textendash}connected nonnegatively curved 4{\textendash}manifolds with circle symmetry},
     journal = {Geometry & topology},
     pages = {3091--3110},
     publisher = {mathdoc},
     volume = {18},
     number = {5},
     year = {2014},
     doi = {10.2140/gt.2014.18.3091},
     url = {http://geodesic.mathdoc.fr/articles/10.2140/gt.2014.18.3091/}
}