@article{SEDP_1974-1975____A4_0,
     author = {Petkov, V. M.},
     title = {Le probl\`eme de {Cauchy} et la propagation des singularit\'es pour une classe des syst\`emes hyperboliques non sym\'etrisables},
     journal = {S\'eminaire \'Equations aux d\'eriv\'ees partielles (Polytechnique) dit aussi "S\'eminaire Goulaouic-Schwartz"},
     note = {talk:5},
     pages = {1--13},
     publisher = {Ecole Polytechnique, Centre de Math\'ematiques},
     year = {1974-1975},
     mrnumber = {402289},
     zbl = {0309.35048},
     language = {fr},
     url = {http://www.numdam.org/item/SEDP_1974-1975____A4_0/}
}