@article{MAN_1913__74_158624,
     author = {G.D. Birkhoff},
     title = {Equivalent {Singular} {Points} of {Ordinary} {Linear} {Differential} {Equations}},
     journal = {Mathematische Annalen},
     pages = {134--139},
     publisher = {mathdoc},
     volume = {74},
     year = {1913},
     zbl = {44.0373.01},
     url = {http://geodesic.mathdoc.fr/item/MAN_1913__74_158624/}
}