@article{10_21136_CMJ_1969_100921,
     author = {Pt\'ak, Vlastimil},
     title = {Openness of linear mappings in $LF$-spaces},
     journal = {Czechoslovak Mathematical Journal},
     pages = {547--552},
     publisher = {mathdoc},
     volume = {19},
     number = {3},
     year = {1969},
     doi = {10.21136/CMJ.1969.100921},
     mrnumber = {0625314},
     zbl = {0185.20701},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1969.100921/}
}