@article{GDZPPN002262223, title = {On the linear differential equation of hyperbolic type}, journal = {Mathematische Annalen}, volume = {65}, year = {1908}, pages = {570-576}, zbl = {39.0427.01}, url = {http://dml.mathdoc.fr/item/GDZPPN002262223} }
Mason, M. On the linear differential equation of hyperbolic type. Mathematische Annalen, Tome 65 (1908) pp. 570-576. http://gdmltest.u-ga.fr/item/GDZPPN002262223/