@article{CMUC_1988__29_1_a8,
     author = {Loebl, Martin},
     title = {Hercules and {Hydra}},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {85--95},
     publisher = {mathdoc},
     volume = {29},
     number = {1},
     year = {1988},
     mrnumber = {937552},
     zbl = {0666.05024},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1988__29_1_a8/}
}