@article{GDZPPN002082721, title = {On permutations involving pairs of twins.}, journal = {Elemente der Mathematik}, volume = {46}, year = {1991}, pages = {78-83}, zbl = {0758.05002}, url = {http://dml.mathdoc.fr/item/GDZPPN002082721} }
Kuczma, Marcin E. On permutations involving pairs of twins.. Elemente der Mathematik, Tome 46 (1991) pp. 78-83. http://gdmltest.u-ga.fr/item/GDZPPN002082721/