@article{MZ_1957__68_169697,
     author = {G.M. Petersen},
     title = {Sequences of {Iterations.}},
     journal = {Mathematische Zeitschrift},
     pages = {151--152},
     publisher = {mathdoc},
     volume = {68},
     year = {1957},
     zbl = {0078.24802},
     url = {http://geodesic.mathdoc.fr/item/MZ_1957__68_169697/}
}