@article{10_21136_CPM_1976_108684,
     author = {Parobek, Ji\v{r}{\'\i}},
     title = {On the number of normal subgroups of a given prime index},
     journal = {\v{C}asopis pro p\v{e}stov\'an{\'\i} matematiky},
     pages = {91--94},
     publisher = {mathdoc},
     volume = {101},
     number = {1},
     year = {1976},
     doi = {10.21136/CPM.1976.108684},
     mrnumber = {0450398},
     zbl = {0344.20022},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/CPM.1976.108684/}
}