@article{JEDP_1990____A20_0,
     author = {Klopp, Fr\'ed\'eric},
     title = {Impuret\'es dans une structure p\'eriodique},
     journal = {Journ\'ees \'equations aux d\'eriv\'ees partielles},
     eid = {20},
     pages = {1--12},
     publisher = {Ecole polytechnique},
     year = {1990},
     mrnumber = {91k:35184},
     zbl = {0707.35125},
     language = {fr},
     url = {http://www.numdam.org/item/JEDP_1990____A20_0/}
}