@article{AIHPA_1973__18_1_57_0,
     author = {Bel, Luis},
     title = {Hamiltonian {Poincar\'e} invariant systems},
     journal = {Annales de l'institut Henri Poincar\'e. Section A, Physique Th\'eorique},
     pages = {57--75},
     publisher = {Gauthier-Villars},
     volume = {18},
     number = {1},
     year = {1973},
     mrnumber = {334814},
     language = {en},
     url = {http://www.numdam.org/item/AIHPA_1973__18_1_57_0/}
}