@article{CMUC_1969_10_3_a4,
     author = {Hor\'a\v{c}ek, Old\v{r}ich},
     title = {\"Uber die {Existenz} einer periodischen {L\"osung} der nichtlinearen {Wellengleichung} in $E_2$ {(Vorl\"aufige} {Mitteilung)}},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {421--424},
     year = {1969},
     volume = {10},
     number = {3},
     mrnumber = {0259324},
     zbl = {0189.15202},
     language = {de},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1969_10_3_a4/}
}