@article{10_4153_CJM_2009_039_2,
     author = {Calin, Ovidiu and Chang, Der-Chen and Markina, Irina},
     title = {SubRiemannian {Geometry} on the {Sphere} {S3}},
     journal = {Canadian journal of mathematics},
     pages = {721--739},
     year = {2009},
     volume = {61},
     number = {4},
     doi = {10.4153/CJM-2009-039-2},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-2009-039-2/}
}