@article{SIGMA_2009_5_a76,
     author = {Peter J. Olver and Juha Pohjanpelto and Francis Valiquette},
     title = {On the {Structure} of {Lie} {Pseudo-Groups}},
     journal = {Symmetry, integrability and geometry: methods and applications},
     year = {2009},
     volume = {5},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SIGMA_2009_5_a76/}
}