@article{JRAM_1965__218_150672,
     author = {Dieter Pumpl\"un},
     title = {\"Uber die {Klassenzahl} imagin\"ar-quadratischer {Zahlk\"orper.}},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {23--30},
     publisher = {mathdoc},
     volume = {218},
     year = {1965},
     zbl = {0129.02304},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1965__218_150672/}
}