@article{AIHPA_1989__51_3_299_0,
     author = {Steinmann, O.},
     title = {On the characterization of physical states in gauge theories},
     journal = {Annales de l'I.H.P. Physique th\'eorique},
     pages = {299--321},
     publisher = {Gauthier-Villars},
     volume = {51},
     number = {3},
     year = {1989},
     mrnumber = {1034590},
     language = {en},
     url = {http://www.numdam.org/item/AIHPA_1989__51_3_299_0/}
}