@article{10_4064_ap_6_3_241_244,
     author = {J. Szarski and Z. Szmydt and T. Wa\.zewski},
     title = {Remarque sur la r\'egularit\'e des int\'egrales des \'equations diff\'erentielles hyperboliques du second ordre},
     journal = {Annales Polonici Mathematici},
     pages = {241--244},
     publisher = {mathdoc},
     volume = {6},
     number = {3},
     year = {1959},
     doi = {10.4064/ap-6-3-241-244},
     language = {fr},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap-6-3-241-244/}
}