@article{JRAM_1976__0283_0284_151726,
     author = {F.W. Sch\"afke},
     title = {Zum {Problem} der {Irreduzibilit\"at} f\"ur zweiparametrige {Eigenwertaufgaben.}},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {182--185},
     publisher = {mathdoc},
     volume = {0283_0284},
     year = {1976},
     zbl = {0347.34022},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1976__0283_0284_151726/}
}