@article{IM_1970__10_142032,
     author = {N.H. KUIPER},
     title = {Minimal {Total} {Absolute} {Curvature} for {Immersions}},
     journal = {Inventiones mathematicae},
     pages = {209--238},
     publisher = {mathdoc},
     volume = {10},
     year = {1970},
     zbl = {0195.51102},
     url = {http://geodesic.mathdoc.fr/item/IM_1970__10_142032/}
}