@article{CMUC_1998_39_2_a6,
     author = {Turza\'nski, Marian},
     title = {On the selector of twin functions},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {303--307},
     year = {1998},
     volume = {39},
     number = {2},
     mrnumber = {1651951},
     zbl = {0938.03068},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1998_39_2_a6/}
}