@article{RCP25_1989__40__19_0,
     author = {Helffer, B. and Sj\"ostrand, J.},
     title = {Periodic {Schr\"odinger} {Operators} with {Constant} {Weak} {Magnetic} {Fields}},
     journal = {Les rencontres physiciens-math\'ematiciens de Strasbourg -RCP25},
     note = {talk:2},
     pages = {19--26},
     publisher = {Institut de Recherche Math\'ematique Avanc\'ee - Universit\'e Louis Pasteur},
     volume = {40},
     year = {1989},
     language = {en},
     url = {http://archive.numdam.org/item/RCP25_1989__40__19_0/}
}