@article{10_4064_ap_4_1_40_60,
     author = {Z. Szmydt},
     title = {Sur l'existence de solutions de certains nouveaux probl\`emes pour un syst\`eme d'\'equations diff\'erentielles hyperboliques du second ordre \`a deux variables ind\'ependantes},
     journal = {Annales Polonici Mathematici},
     pages = {40--60},
     publisher = {mathdoc},
     volume = {4},
     number = {1},
     year = {1957},
     doi = {10.4064/ap-4-1-40-60},
     language = {fr},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap-4-1-40-60/}
}