@article{AIHPA_1992__57_4_361_0,
     author = {Yafaev, D. R.},
     title = {On the scattering matrix for perturbations of constant sign},
     journal = {Annales de l'I.H.P. Physique th\'eorique},
     pages = {361--384},
     publisher = {Gauthier-Villars},
     volume = {57},
     number = {4},
     year = {1992},
     mrnumber = {1198982},
     zbl = {0780.47011},
     language = {en},
     url = {http://archive.numdam.org/item/AIHPA_1992__57_4_361_0/}
}