@article{JRAM_1992__425_153398,
     author = {R. Mennicken and M. M\"oller and H. Langer},
     title = {On {Floquet} eigenvalue problems for first order differential systems in the complex domain.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {87--122},
     year = {1992},
     volume = {425},
     zbl = {0752.34004},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1992__425_153398/}
}