@article{SJL_1964___1_20_0,
     author = {Leray, Jean and Ohya, Yujiro},
     title = {Syst\`emes lin\'eaires, hyperboliques non stricts},
     journal = {S\'eminaire sur les \'equations aux d\'eriv\'ees partielles},
     pages = {20--71},
     year = {1964},
     publisher = {Coll\`ege de France},
     number = {1},
     language = {fr},
     url = {https://www.numdam.org/item/SJL_1964___1_20_0/}
}