@article{JRAM_1970__245_151065,
     author = {Joseph Warren},
     title = {Annular functions.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {143--148},
     year = {1970},
     volume = {245},
     zbl = {0203.07503},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1970__245_151065/}
}