@article{SIGMA_2009_5_a85,
     author = {Stefan Haesen and Leopold Verstraelen},
     title = {Natural {Intrinsic} {Geometrical} {Symmetries}},
     journal = {Symmetry, integrability and geometry: methods and applications},
     year = {2009},
     volume = {5},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SIGMA_2009_5_a85/}
}