@article{IM_1982__69_142950,
     author = {Joel Langer and David A. Singer},
     title = {Diffeomorphisms of the {Circle} and {Geodesic} {Fields} on {Riemannian} {Surfaces} of {Genus} {One.}},
     journal = {Inventiones mathematicae},
     pages = {229--242},
     publisher = {mathdoc},
     volume = {69},
     year = {1982},
     zbl = {0508.58010},
     url = {http://geodesic.mathdoc.fr/item/IM_1982__69_142950/}
}