@article{ELMA_1991__46_2_141506,
     author = {Marcin E. Kuczma},
     title = {On permutations involving pairs of twins.},
     journal = {Elemente der Mathematik},
     pages = {78--83},
     publisher = {mathdoc},
     volume = {46},
     number = {2},
     year = {1991},
     zbl = {0758.05002},
     url = {http://geodesic.mathdoc.fr/item/ELMA_1991__46_2_141506/}
}