@article{AM2_1968__1_135969,
     author = {H. Schwerdtfeger},
     title = {Involutory {Functions} and {Even} {Functions.} {(Short} {Communication).}},
     journal = {Aequationes mathematicae},
     pages = {210--210},
     publisher = {mathdoc},
     volume = {1},
     year = {1968},
     zbl = {0176.46104},
     url = {http://geodesic.mathdoc.fr/item/AM2_1968__1_135969/}
}