@article{SEDP_1989-1990____A4_0,
     author = {B\"attig, D.},
     title = {A directional compactification of the complex {Fermi} surface and isospectrality},
     journal = {S\'eminaire \'Equations aux d\'eriv\'ees partielles (Polytechnique) dit aussi "S\'eminaire Goulaouic-Schwartz"},
     note = {talk:4},
     pages = {1--9},
     publisher = {Ecole Polytechnique, Centre de Math\'ematiques},
     year = {1989-1990},
     mrnumber = {1073179},
     zbl = {0716.35082},
     language = {en},
     url = {http://www.numdam.org/item/SEDP_1989-1990____A4_0/}
}