@article{UM_1995_3_3_a17,
     author = {Calda, Emil},
     title = {Kter\'a to jsou l\'eta?},
     journal = {U\v{c}itel matematiky},
     pages = {62--63},
     year = {1995},
     volume = {3},
     number = {3},
     language = {cs},
     url = {http://geodesic.mathdoc.fr/item/UM_1995_3_3_a17/}
}