@article{MM2_1974__13_154258,
     author = {Vlastimil Pt\'ak},
     title = {A {Theorem} of the {Closed} {Graph} {Type.}},
     journal = {Manuscripta mathematica},
     pages = {109--130},
     publisher = {mathdoc},
     volume = {13},
     year = {1974},
     zbl = {0286.46008},
     url = {http://geodesic.mathdoc.fr/item/MM2_1974__13_154258/}
}