@article{MAN_1877__11_156748,
     author = {Cayley},
     title = {On the theory of {Partial} {Differential} {Equations}},
     journal = {Mathematische Annalen},
     pages = {194--198},
     year = {1877},
     volume = {11},
     zbl = {09.0259.01},
     url = {http://geodesic.mathdoc.fr/item/MAN_1877__11_156748/}
}