@article{AM2_1984__27_137027,
     author = {Ulrich Abel},
     title = {A note on the parameters of rational iteration groups.},
     journal = {Aequationes mathematicae},
     pages = {236--241},
     publisher = {mathdoc},
     volume = {27},
     year = {1984},
     zbl = {0561.54031},
     url = {http://geodesic.mathdoc.fr/item/AM2_1984__27_137027/}
}