@article{SIGMA_2009_5_a38,
     author = {Juan A. Calzada and Javier Negro and Mariano A. del Olmo},
     title = {Intertwining {Symmetry} {Algebras} of {Quantum} {Superintegrable} {Systems}},
     journal = {Symmetry, integrability and geometry: methods and applications},
     year = {2009},
     volume = {5},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SIGMA_2009_5_a38/}
}