@article{JRAM_1986__365_152805,
     author = {R. Sch\"afke and H. Volkmer},
     title = {On the reduction of the {Poincar\'e} rank of singular systems of ordinary differential equations.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {80--96},
     publisher = {mathdoc},
     volume = {365},
     year = {1986},
     zbl = {0569.34037},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1986__365_152805/}
}