@article{MAN_1978__238_163191,
     author = {Peter Lappan},
     title = {On the {Normality} of {Derivatives} of {Functions.}},
     journal = {Mathematische Annalen},
     pages = {141--146},
     year = {1978},
     volume = {238},
     zbl = {0372.30023},
     url = {http://geodesic.mathdoc.fr/item/MAN_1978__238_163191/}
}