@article{PMFA_1971_16_6_a2,
     author = {Folta, Jaroslav},
     title = {Je\v{s}t\v{e} o {Keplerovi}},
     journal = {Pokroky matematiky, fyziky a astronomie},
     pages = {286--288},
     year = {1971},
     volume = {16},
     number = {6},
     language = {cs},
     url = {http://geodesic.mathdoc.fr/item/PMFA_1971_16_6_a2/}
}