@article{MAN_1912__72_158572,
     author = {G.D. Birkhoff},
     title = {Note on the {Expansion} of the {Green's} {Function.}},
     journal = {Mathematische Annalen},
     pages = {292--294},
     publisher = {mathdoc},
     volume = {72},
     year = {1912},
     zbl = {43.0400.02},
     url = {http://geodesic.mathdoc.fr/item/MAN_1912__72_158572/}
}