@article{MM2_1971__5_154066,
     author = {G\"unter Frank and Erwin Mues},
     title = {\"Uber den {Index} der {L\"osungen} linearer {Differentialgleichungen.}},
     journal = {Manuscripta mathematica},
     pages = {155--164},
     publisher = {mathdoc},
     volume = {5},
     year = {1971},
     zbl = {0237.34016},
     url = {http://geodesic.mathdoc.fr/item/MM2_1971__5_154066/}
}