@article{PMFA_1980__25_5_a1,
     author = {Ullmann, Vojt\v{e}ch},
     title = {Gravita\v{c}n{\'\i} energie},
     journal = {Pokroky matematiky, fyziky a astronomie},
     pages = {250--259},
     publisher = {mathdoc},
     volume = {25},
     number = {5},
     year = {1980},
     language = {cz},
     url = {http://geodesic.mathdoc.fr/item/PMFA_1980__25_5_a1/}
}